The obvious choices:
Shenmue 2
Metal Arms
Prince of Persia: Sands of Time
Not so obvious:
Freelancer, it was a great start, a sequel with a richer universe to explore (just more variety in what you can do) would be awesome
Will it happen? Doubt it, space sims are out :-/
Speedball 2, this probably belongs in obvious, i think it's time future sports made a brutal comeback.
Will it happen? I was assured it would happen eventually, maybe if that rollerball remake hadn't sucked so hard we would already be playing it.
Total Annihilation, taught a generation of people how to spell Annihilation, best RTS ever and all it got was that shitty Kingdoms sequel Chris Taylor wasnt even involved in :'(
Will it happen? Uh Huh, thanks to EA and Gas Powered Games, Taylor will be delivering a new RTS in 2006. Though it won't be called TA2, the TA license is owned by Atari.