Hate Sacred. Loved Diablo 2. Sacred is NOT a good Diablo 2 clone in my opinion.
Hellgate London is NOT like Diablo 2. Hellgate London stunk for me as well.
Titanquest was adequete.
Dungeon Siege 2 was perhaps the best D2 clone for a computer overall, if one doesn't get stuck on Graphics. Excellent, though in someways it's the best D2 clone because...it copies D2 in many ways.
At least best D2 clone on PC.
I'd say the best games that are Diablo 2 clones actually have come out on consoles in the past few years. The Snowblind series of games are good candidates inclusive of the Baldurs Gate, Justice League Heroes, and Champions of Norrath.
In particular, Champions of Norrath is hands down THE BEST Diablo 2 clone type game out there in my opinion. It's also only going to play on a PS2 or PS3.
If you like superheroes, you can also get Ravensoft's clone of that type of game, into the X-men universe with X-men Legends, though for PC only X-men Legends 2 came out. Following suite, but diverging from the straight Diablo 2 type clone, is Marvel Ultimate Alliance which changes things up from the standard formula a little, but still quite good.