I hope this isn’t considered thread shitting but prepare to be dissapointed. People look at Diablo 2 through rose colored glasses, any game that tries to copy it too closely is going to seem boring and repetitive because thats exactly what it was. If you get bored of d2 fast then something thats almost the same will have the same effect.
I didn’t get bored of Diablo 2 “really fast”, I spent hundreds, if not thousands, of hours playing D2 from release to about 2004 or so. There’s a reason Diablo 2 is one of the best selling computer games of all time, and almost every message board has a “Games like D2?” thread. It was almost perfectly balanced. You had your fast paced, almost arcade-like action, but an absolutely ridiculous amount of freedom in item and skill choices. Every character had methods of dealing with both single enemies and large hordes. Every character had at least 2-3 different builds that worked well, and some oddball builds that worked less well but were still fun (Buriza Werebear!) . It also had a good pvp system, which I didn’t get as much into but was cool once in a while. And playing online was awesome. I remember back in the beginning before everyone had the good uniques, I was just just starting to play online. We were fighting an act boss, I forget which one. It was just wiping people out left and right. We had a full team, and open tp’s nearby. People were just rushing in and dying. A few people left, and a paladin came in with some aura that really helped us. Finally, the bosses health wore down to a sliver. “Come back now!” people were typing. He/she/it finally crashed to the ground, slain, and a huge cheer and a chorus of "gj"s went up. That’s when I realized there was something special there.
You can bitch about imbalances, chaters, rushers, spammers, scammers, etc, and yes D2 did have its flaws (most of which could’ve been fixed) but the fact is I’ve never had any other game that gave me quite that same rush as Diablo 2 did at its peak (I would say 1.07 or 1.08).
The reason most people stop playing D2 after a while is, well, you just run out of stuff to do. I’ve taken at least 2 of every class up to level 90 or beyond, and have pretty much done everything in the game there is to do. There’s only so many times you can play the same game no matter how good it is. I think Blizzard is reluctant to work on the third game in the series because they do have a lot to live up to. It’s not like RTS or FPS, where there’s dozens of great games within those categories. D2 hit a rare sweet spot that nothing else has ever been able to match, and the few that have tried have failed miserably. Titan Quest is the only thing I’ve played that’s come close to giving me that “D2 rush”, and I would have loved to see what Iron Lore could’ve done with TQ2 but that’ll never happen now.
Cliver Barker’s Undying, maybe? Unreal Gold, or Unreal 2? (Or even the tournament might fit your needs, if you just want to slay things.) Here is the anthology. For the Playstation, try the God of War series.
I’m with you, Apocalypso. I spent waaaaay too much time playing D2. The only thing that broke me free was transferring my addiction to Morrowind. I’ve been back a few times, but the graphics just don’t do it for me anymore – I want higher resolution these days.
My current addiction (4 years now) is City of Heroes. It has many of the same great qualities as D2, although it’s totally different setting and engine, so it appeals to the same parts of me that D2 did.
I’m surprised nobody has mentioned MYTHOS yet. It’s now in closed beta, but will be open very soon.
It was originally designed to test the game engine for Hellgate: London. The developers had a blast with it, so they kept it running. It’s litterally Diablo 3 - plays likd D2, designed like WoW, actually really fun! 
It is going to be totally free, with a plan for Microtransactions for in-game kitsch in the future.
Enjoy! ( I really recommend this game for all D2 / WoW fans. Very well done indeed. And free!)
Yo. Check out post #15.