I'm actually gonna say items are most important. Diablo 2 had the best replay of any video game I've ever played. I mean, you picked your character and skill set and made it to end game like any MMO. But, let's compare D2's endgame to WoW's endgame. WoW, you raid for hours for...hell not shit of an improvement. I mean as soon as I hit 70 in the BC, I went to battlegrounds and frequently got the highest damage because class mattered a hell of a lot more than equipment. There was a famous orc shaman who beat ass with nothing but trinkets and a weapon, because the meager stat boosts from equipment just did not affect the game. It was the equipment in WoW that made me stop playing, because I got to endgame, I looked at the stuff I could get and thought "shit, none of this is worth the time, I'm gonna go whoop some PvP ass before my subscription runs out". And thus Blizzard lost my subscription due to clusterfucks over +2 stamina.
I went back to playing Diablo after checking out arreat summit and seeing awesome new runewords and charms. "What's that, I can shoot out Diablo's firestorm like a machine gun as a werewolf and do 400% increased damage with my shield slot? That's like 2,000% increased damage, fuck you Baal." To think I used to worry about 15 spell damage instead of "+4 to spell ranks".
In fact, if not for the thousands of hammerbots that took over D2, I'd still be playing it. So I can't wait for D3 to provide a fresh, unexploited start. Although, if I get to endgame and find they've been taking tips from WoW with their equipment, well I'll just have to find me a new game.