SabreWing 2
This one's a bit strange. The demo streams through your web browser. Joystick support seems poor, if nonexistent. The storyline seems pretty linear: destroy the evil aliens before they destroy you. Only 16 missions. Also, the Wild Tangent control panel that allows you to play the game on the Net conflicts with other software, most notably, Echelon.

On the plus side, though, the game's graphics are excellent and the flight model responsive, even over the Net. The controls are easy to figure out, though I really miss joystick support. Hopefully the full version has it, but I'm not quite convinced enough to take the leap.

SabreWing 2 Home Page