I just wish you could change your class in ME1 after every NG+. I'm missing most of the achievements, because I never bothered to make a "fresh" character. Once I got the best weapons/mods, I didn't feel like going through the campaign with stock gear again.
I only did one "New Game+" on Mass Effect...I've played through it with 4 different Shepards, though. That's 5 times through the game.
I like what Mass Effect 2 did - if you played it again, you got a bonus in money and minerals.
http://www.youtube.com/watch?v=pMKUUUvjjzo Fan of: Steelers(6-time Champions), Red Wings(11-time Champions)
My favorite is something Persona 4 did and that was dropping my characters levels back down to lvl.1 but I got to keep al my items, money, persona compendium, etc. Of course, I also like Borderlands 2 where the enemies increase in level at NG+.
Some games also really could have used a NG+, for example The Witcher 2. I get all those good items in the last hour of the game and I barely get to use them. NG+ would have been a great feature to add. Before anyone says anything, they wouldn't have to use this feature if they don't want to, it would have just been a nice addition.
"I have two rules I follow. The first, never kill someone without a reason. The second, you can always find a reason to kill someone." - Saren