I think there's definitely a market for shareware. Have a look at the Independent Games Festival entries. Many of those were really cool and have even sold. Some even became big hits like Alien Hominid and Gish.
Granted, at first a glance, these are not your everyday games but when you give them a good look, you'll find that they're are reallly not so special. Alien Hominid, in its basic form a simple horizontal shooter. And Gish, a mere platform game. Sure, they're briliantly adapted to give gamers new gameplay but in essence they're still remakes of old games.

Trick is, like Dirk said, to find an idea that has never been done or thats only been done a few times. Create a game that has been done a thousand times and you'll find that people are going to be less interested. (no offence intended firlefanz)