I also had an interest in GRID (which I still ain't played, actually).
If you liked/wanted Dirt 2, I think you'll like/love GRID. Imo it's the best arcade-y racer in the last decade (on PC at least), though Burnout 3 stands similarly high in a different way. The physics model in GRID is so enjoyable, a nice balance of depth and fun.
For reference, my opinions of known titles (100% completion or close unless noted):
NFS: Underground : okay
NFS: Underground 2 : Fun.
NFS: MW : Much Fun.
NFS: Carbon : Enjoyable, ranks a little under NFS:U2
NFS: ProStreet: skipped
NFS: Undercover : Dull waste of time... throw me a challenge here... I'm not used to getting 1st place on my first attempt most of the time.
NFS: Shift : Didn't like... supposedly there's something interesting if you tweak all the setting away from the completely stupid defaults (e.g. cars seem featherweight)
NFS: Hot Pursuit (2, 2010) Much Fun
NFS: Shift 2 : Backlog
NFS: The Run: Enjoyable, but hard to recommend. Quite pretty, but 30 FPS cap. Damn stupidest thing is the rare gas station method of switching cars... too rare, impossible/hard to know what kind of car (muscle/steet racer/exotic) to pick to handle the next several tracks/segments.. and switching cars sets you back a few seconds. Minor gripe: a few forced-in quick-time-events (in cutscenes, not in driving). Also annoying is the ability to replay by chapter, a string of ~5 segments.
Burnout Paradise: Fun/Enjoyable... I wish it was more challenging though. Pretty.
Burnout 3, 4, 5: Awesome... I liked the challenge of 3 the best.
Dirt : Backlog... need to boot to XP or check into fixes for Win7 compatability, supposedly good
Dirt 2: Excellent (And I hadn't been a fan of offroad racers.)
Dirt 3: Backlog /shame (though since good/decent racers are one-a-year at best I like to keep something in reserve)
GRID: Most Excellent, edges out Dirt 2. Much replayability. I wish they made a sequel/expanion (just give me more tracks/cars. I especially liked Nürburgring (the Bahrain track was memorable too).
Split Second: Much fun. The gimmick set-destruction is very very well integrated and mastery of is critical to getting 1st place. Unfortunately, I've played 2/3 though three times... my saves get horribly corrupted. (Despiite rolling back to prior saves: GoGo Dropbox restore w/Link Shell Extention -- I should post about that separately). I want to finish this sometime by not exiting it before completion.
Driver: SF : It's a car themed game, not a racer, imo. I didn't like it that much... though some of that is disappointment from expecting more of a racer. The shift mechanic is novel.
Flatout 1/2/UC : Backlog
Midnight Club II: Played an hour... didn't grab me