Wikipedia has the following for Ridge Racer:
"The game features a total of 24 courses (12 unique courses and the same 12 courses reversed) all taken from previous PlayStation games or the arcade-only title Rave Racer, and 54 unlockable (fictional) cars. "
And Ridge Racer 2:
"The game features a total of 42 tracks (21 unique tracks and the same 21 tracks reversed) - two tracks from Ridge Racer (these tracks also appeared in Ridge Racer V), three tracks from Ridge Racer Revolution, four tracks from Rave Racer, eight tracks from R4: Ridge Racer Type 4, and four tracks from Rage Racer. Every track from every Playstation Ridge Racer game is included as part of this package. The game also features a total of 62 fictional cars, including 4 Special Class cars. As you win races, you unlock faster cars."
I don't own either but I have been debating about the same thing as you. From what I read and others told me, Ridge Racer 2 is more like an add-on or expansion, since its the same exact game as the first one.