Mario Kart? Not a chance. Too much mode 7 and it has a DSP chip for the graphics - IIRC my old Celeron 300 couldn't handle it (but could everything else). It'll run but it won't be playable...of course I could be wrong. Try it anyway...I heard F-Zero runs perfect under certain conditions. Then again, it didn't have that special DSP thing...
I'd take a close look at every system emulated really. C64 has tons of great games, probably equal to or greater than NES in quantity (because publishing was cheaper back then and people thought paying 3 times as much for a console game was rediculous). Go to any site and you'll find plenty - try www.lemon64.com or something, there's too much to mention here, but I will say everyone loves Kikstart (it's like Excitebike only better) and Boulderdash. Commodore Plus/4 has a few good games too. I'd probably recommend Dork's Dilemma (Bomberman sort of game, but very different), Jetbrix and hmm...Mr Puniverse?
ZX Spectrum's another good machine. Again, like C64, tons of games. Graphics and sound are simplified in comparison, but most games are ports from one of the two machines to the other. Plenty of good games again, like NES. I'd probably recommend the usual stuff...Manic Miner, Jet Set Willy 1/2, the Ultimate/Rare games, the 7 Dizzy games and 2 Seymour games, etc.
Atari ST...personally I haven't put the emulator on because I don't have the space and I haven't really tried. But I want to. The machine is often compared to an Amiga, because a lot of games for Amiga were ported from the ST. I dunno what runs, but I'd check out stuff like APB, Double Dragon, Pang, and Turbo Outrun.
MSX1/MSX2 is great for early Japanese games. ESPECIALLY if you're a fan of Konami games. Do I really need to name what's on this system? I guess I do. I recommend trying Metal Gear 1/2, Snatcher (but it's not translated yet), SD-Snatcher (this is translated), Vampire Killer, Goonies, Antarctic Adventure, Penguin Adventure, Parodius, Knightmare, Maze of Galious, the Nemesis games, and so on. A lot of these games were on other systems (NES, SNES, Spectrum) but they were designed for MSX and that's what they're best on.
In brief, for other consoles:
Atari 2600: Anything. You either like it or you don't.
Coleco: Arcade ports. Not much else unique to the system...
GB/GBC: Galaga. There's more but games are so hard to find for these now!
NES: I think everyone knows what's on this.
PC Engine: Sega arcade ports, Bomberman, Parodius.
SMS: Phantasy Star, Golden Axe Warrior, Golvellius. All good RPG's. Fantasy Zone 1 and 2 also. Oh, and Wonderboy 3.
Wonderswan: Does this save games? If so try Final Fantasy 1, 2 and maybe 4 on it. They run perfectly. I just don't remember if it saves!
Other: There's plenty of nice home made games on GP32. The best things are the ports, though, if you ask me...