But the majority of the sellout 35,048 crowd left Upton Park deflated after Hammers squandered a 2-0 lead to their London rivals, having also missed a penalty chance to make it 3-1 with 15 minutes remaining.
A heartbreaking end to an otherwise fine performance that deserved all three points.
Joe Cole, a Gunners fan as a boy, shot Hammers in front a minute before half-time with a first-time, left-footed shot from the edge of the box after Fredi Kanoute had crossed from the left flank.
It was no more than West Ham deserved for having the temerity to mount wave after wave of attacks on the blue-shirted visitors, who were retreating in numbers. With Michael Carrick and new signing Edouard Cisse dominating the centre of midfield, Joe winning the battle of the Coles on the right flank (Ashley rarely got forward), and Kanoute and Jermain Defoe proving a constant handful for Sol Campbell and Martin Keown, Hammers were unrecogniseable from the side that capitulated so poorly at Newcastle on Monday.
Arsenal have not lost a league match since December 18, 2001, but they seemed doomed here when, nine minutes after the interval, strikers Defoe and Kanoute combined to make it 2-0.
Defoe, working his socks off, chased a loose ball from Cole that he just managed to keep in play on thre right flank. His driven cross caught Arsenal's back four flat-footed and there was Kanoute arriving at the near post, ahead of Keown, to prod the ball past David Seaman in front of the Bobby Moore Stand. Cue wild scenes of jubilation.
In the space of three minutes, Kanoute could have scored a hat-trick, but his low left-footer was saved by Seaman and then the Frenchman - recovering from the neck strain that ruled him out of the Newcastle defeat - drilled a right-foot shot just a foot beyond the far post from 18 yards.
Arsene Wenger used all three of his subs in an effort to turn the tide but it seemed a forlorn hope when Joe Cole wriggled into the penalty area on 75 minutes and was tripped by his namesake. Arsenal reacted furiously to referee Neale Barry's decision and there was some pushing and shoving between Lauren and Joe that delayed the taking of the spot kick.
Kanoute, who skied the best chance of the first half high into the upper tier of the Centenary Stand, did the opposite this time. He won't want to see a replay of a penalty that barely had the power to reach Seaman's goalline before the England keeper fell on the ball down by his right-hand post. He won't save an easier spot kick.
Having wasted such a great chance to put the game beyond the champions, one sensed that Hammers would pay the price.
Kanu, an effective half-time replacement for Dennis Bergkamp, caused problems but it was last season's Premiership top scorer, Thierry Henry, who netted their first goal, 10 minutes before Kanoute's howler. The Frenchman turned Christian Dailly 20 yards from goal before unleashing a brilliant, unstoppable shot past David James and into the top corner of the net.
It was cruel on James, who had twice foiled Henry and also denied Sylvain Wiltord with fine saves in the first half.
Wiltord would have the last word, though. Cutting inside from the left, he played a neat one-two with Kanu on the edge of the box before curling his shot past James for the equaliser in the last minute of normal time.
Typical Arsenal...typical West Ham.
Desperately disappointed though they are entitled to be, Hammers had James to thank for a fantastic block in the dying seconds of time added on to deny Kanu, after sub Gary Breen - on for Nigel Winterburn - inexplicably tried to head a low cross that only presented the Arsenal striker with the chance to snatch an ill-deserved winner.
One point after two games is far from ideal but on the evidence of this exhilirating performance, Glenn Roeder and his players should retain the confidence and belief that another good season is on the cards...
Minute-by-minute:
8 - After a relatively quiet start, Arsenal come close to open the scoring when Bergkamp's clipped pass releases Henry, who fires his left foot shot just inches wide of the post.
11 - After good link-up play between Cisse and Joe Cole, the ball is slipped in behind Keown but Seaman is quick off his line to deny Kanoute.
15 - Henry goes close again, turning Repka before bearing down on goal and curling in a shot that James holds well.
16 - Collecting a long pass on his chest, Sinclair turns and fires in a blistering right foot shot that beats Seaman but crashes off the post and back into play before being cleared.
17 - Bergkamp BOOKED for a foul on Joe Cole.
28 - After Kanoute does extremely well to hook back Cisse's crossfield pass from the byline, Defoe collects the ball and hammers a scorching effort just over the bar.
32 - A move made in France almost gives Hammers the lead, as Cisse's delightful pass releases the overlapping Schemmel, who cuts the ball back for Kanoute. Sadly, the striker blasts his shot high over the bar.
35 - Kanoute misses another excellent chance again, as the impressive Cisse flights a delightful ball over the top of the defence for his fellow countryman, who delays an early attempt and sees Seaman gather.
42 - Edu BOOKED for a foul on Sinclair.
43 - Henry's clever pass releases Wiltord in the box, but James is off his line quickly to smother the ball.
44 - GOAL! West Ham's first goal of the season arrives at an ideal time and from a unfamiliar source...Joe Cole! Carrick's excellent work under pressure allows Sinclair to gain possession and find Kanoute on the left. The Frenchman's low cross rolls along the edge of the penalty area to the far side, where Cole is waiting to fire a low left-foot shot past the despairing dive of Seaman and into the bottom corner for his first league goal since May 2001. West Ham United 1 Arsenal 0.
Added time: 1 minute.
Half-time: West Ham United 1 Arsenal 0.
Second Half:
46 - Substitution for Arsenal, Kanu replaces Bergkamp.
53 - Ashley Cole BOOKED for a foul on Schemmel.
54 - GOAL! The Hammers grab a superb second, thanks mainly to the determination and endeavour of Jermain Defoe. Schemmel's misplaced pass appears to be heading out of play, but the young striker races to keep the ball in and whips in a magnificent first time cross to the near post, where Kanoute gets in front of Keown to toe-poke the ball past Seaman. West Ham United 2 Arsenal 0.
55 - It's almost two for Kanoute, as Cole's glorious pass releases the Frenchman, but his left-foot shot is just kept out by the hand of Seaman.
57 - The Hammers are on fire and Kanoute is in the thick of things again, collecting possession in the penalty area after a flowing move and firing a shot just inches wide of the far post.
62 - Substitution for Arsenal, Pennant replaces Parlour.
63 - Repka BOOKED for a foul on Henry.
65 - GOAL. Arsenal strike back out of the blue with a simply wonderful goal from Thierry Henry. The French striker receives the ball with his back to go some 30 yards out before turning Dailly with a simple flick and unleashing a blistering right foot shot that flies past James in to the top corner. West Ham United 2 Arsenal 1.
68 - Keown BOOKED for a foul on Defoe.
70 - Substitution for West Ham, Breen replaces Winterburn.
74 - After good work from Defoe, Joe Cole collects the ball and wriggles into the penalty area before being brought crashing to the ground by a challenge from Ashley Cole. Referee Barry immediately points to the penalty spot.
74 - Vieira BOOKED for dissent.
75 - Kanoute steps up to take his first ever penalty for West Ham, but the lack of power in his kick enables Seaman to comfortably gather the ball low down at his right hand post.
84 - Substitution for Arsenal, Toure replaces Lauren.
84 - Substitution for West Ham, Moncur replaces Joe Cole.
87 - Moncur BOOKED for a foul on Wiltord.
89 - GOAL. Absolute heartbreak as Arsenal snatch a late, late equaliser. Wiltord slips a pass into Kanu in the area and then follows up to collect a return before firing the ball past James from 10 yards out. West Ham United 2 Arsenal 2.
Added time: 3 minutes.
90 - Henry's curling free-kick from 25 yards out is deflected goalwards before James magnificently tips the ball over the bar for a corner.
90 - James once again comes to the rescue, throwing himself at the feet of Kanu after Breen fails to clear a low cross.
Full-time: West Ham United 2 Arsenal 2.