They can be used in any games that have support for racing wheels. Whether or not it's worth it is up to you, I would say if you are a casual racing gamer, just get a controller. That's a really good middle ground between the keyboard and the wheel.
I just purchased a used Thrustmaster TMX Pro with the 3 pedal setup and a stand. I really enjoy it, and it's night and day between that and using a controller. I mainly play Forza games, but I have a few other racing/sim games that I use it with. The only problem I have with mine is that I don't like the feel of the plastic on the top and bottom of the wheel, but the mechanics are great, the pedals work perfectly and feel great, and the price was right.
I would say if you are budget...