I don't really follow, what exactly would the Crazy Taxi licence get you? It's Sega's IP and they just localized and published the game on PS2 so I don't really see how that would be worth anything. I mean they have plenty of stuff up there that they don't own like Bust A Move (Puzzle Bobble), bunch of Midway stuff like Mortal Kombat, Smash TV, and NARC, X-Men Children of the Atom from Capcom, the Worms games from Team 17. What exactly are people buying?
The only thing that's worth a damn is Extreme G, I like that series even though it wasn't great or anything it was a good rental budget release. If GameTap or MS was smart they'd buy up some of these retro games and pimp them out for XBLA. Also Iggy's Wreckin Balls was kinda cool, I picked it up for like $5ish and it was worht it.