Okay, I picked up the Xbox version earlier.
Hmm, flickering shadows in MKII and 3 bug me. It's like that string of MAME versions where the shadows were screwed up. The sound effects are fine in both games (with 3 having better sound, which it should) but the music stopped in a couple of matches on II, and I didn't notice any problems with 3. The games control exactly the same as in the arcades. Other than the shadows and the occasional sound problem, the games are perfect.
Narc was awesome, just for how hillariously bad it was. Not gameplay wise, which was good, but the goofy look of it all. The drug sellers, the addicts that threw heroin needles at you, the freaked out clowns... The sounds effects were great.
Primal Rage seemed arcade perfect to me.
Gauntlet II was fucking annoying. THOSE DAMN SOUND EFFECTS MY GOD. The gameplay bit ass as well. I didn't remember the game being that bad when I played it last in... oh... 1987?
Arch Rivals was a piece of shit. I'm sorry. Spy Hunter II: crap.
Total Carnage was awesome. There were soooooo many sprites on the screen at all times, and absolutely no slowdown.
Rampage World Tour was fun as hell! My friend and I played that for such a long time. Probably over 45 levels completed, and we weren't even halfway through the game it seemed like.
We didn't really play any of the other games yet. One thing I can say is how consistantly good the graphics look. I don't know if it's a product of upconverting to 1080i or what, but I expected all these 2D games were going to look like pixelicious shit. They don't! They look wonderful!