I have tried to add a few here with more of general consensus opinions or my own opinons. Can't think of any more for now.
Good:
Diablo 2 - Built upon a solid game with extra goodies and a secure server which reduced hacking and nasty stuff which plagued Diablo 1 (well, it worked for a little while anyway)
Mechwarrior 3 - Mech 2 was legendary, Meach 3 brought along a good story, great narration and the best Mech experience to date.
Bad:
Mechwarrior 4 - They took a look at a successful Mech 2 and Mech 3 then decided not to follow their formula for a good game.
Need For Speed Underground 2 - From what I gather, most people will disagree with this but I found NFSU2 to be pretty crap compared to NFSU1. Didn't enjoy it one bit... mind you, I didn't really play much NFSU once I picked up Most Wanted
Aliens Vs. Predator 2010 - Take a great game, lose some of the atmosphere, give it certain features which means that console players can play and have a cinematic experience... They removed the heart and soul of the game and ripped out the essence of being a Colonial Marine. A Marine has firepower and can take down an Alien with a mere 1 or 2 bullets from a pulse rifle... yet is so fragile, that the merest blip of his motion detector registering causes panic.
Mixed Opinions:
Dawn of War 2 - Whilst I think Relic are at the forefront of cutting edge ideas in the RTS market and unmistakably the best creators of RTS games over the past decade (and slightly beyond), Dawn of War 2 has received mixed opinions as to how good it really is. I love the RTS/RPG system ever since I found a rather crap game called Rage of Mages. The second iteration of this lost some of it's epicness through a reduction in model numbers, specifically Space Marines, to try and bring it a little more in line with WH40k fluff aka. Imperial Propaganda
Fallout 3 - Taking a classic 3D isometric game with real time movement and turn based combat and transforming it into a first/third person shooter with stats and an optional turn based combat element was never going to be easy. Personally I enjoyed Fallout 3 for what it was, a good and solid game which was only let down by a completely pants story element.