fitness evolved will give you a "light" work out which is ok when you are first starting out but can end up being a little easy after a while.
active sport 2 will push you. it will make you sweat but it will also make you shout and yell at the screen because of all of the issues with the tracking. (
http://forum.ea.com/eaforum/posts/list/120/3877266.page#12043303) if you can get it cheap, all the better.
sports if fun, and will also give you a good work out. boxing rocks
since starting to use a combination of all of the above, and improving my diet I have:
1. Lost 2 stone in weight.
2. Gone from an 18 inch to a 16 inch collar
3. Down to a 34 inch waste from a 40 inch waste.
All of this since Jan.