If you are looking for a realistic Rally Sim, RBR is pretty much the only one to get these days, even though it is a few years old now. Good news though, you can pick it up for next to nothing these days (but you may need to search EBay for it). The driving model in RBR is brilliant, but certainly not easy, it takes some time to learn to drive it well. Once you can drive this Sim, you will understand why the others are so far behind. RBR has recently been rated as one of the all time best Racing Sims, and it lives up to that rating.
RBR has been upgraded and expanded by after market developers, so mods such as RSRBR2010 adds a massive amount of additional content, and enables us to run on-line rally events here at Racedepartment.
Check out some of the movies here:
http://www.racedepartment.com/richard-burns-rally/20046-rbr-movies.html
That will give you some idea of how the game looks, and we have some promo videos showing the types of Rallys we run every week on-line.
As Eckhart has advised, the next best rally Sim is Rally Trophy which is even older, but doesn't have the support that RBR has.