NFS doesn't have much substitutes.A few that I can think off is Test Drive Unlimited,Flat Out 2,Colin McRae's DiRt & GTR 2 but none of these games are much similar to NFS's gameplay.
nfs, colin mcrae games (cmr) & GTR2 are all of different categories.
1 is fully blown arcade, other's a rally game & the last one's a mod friendly fully blown sim.
nfs like games = Flat Out, crashday, grid, juiced
, mid night club 2 (old),...
dont buy/ d/l cmr or gtr2 type of games unles you've interest in WRC/rally or track racing.