If you are looking for a very well made, easy to use 2.5D game engine,
then FRB is it. It is bar none the best 2.5D engine out there for XNA.
Not only that, but it is free, and very well supported! Have a look at
my web site, for the latest on the game I started from scratch using
FRB engine.
If you are making a game using XNA, then FRB is a must to check out.
http://www.flatredball.com/frb/blog/