I loved NFS 3 (Hot Pursuit), NFS 4 (High Stakes), NFS 7 (Underground) and NFS 15 Shift 2 Unleashed. Still have a soft spot for NFS 2, though couldn't play it any more.
In the avg but good bin are NFS 9 Most Wanted, NFS 10 Carbon and NFS 11 Pro Street. I would put NFS 13 Shift in here, but it had odd handling (fixed in Shift 2) making it instantly forgettable.
On the bad pile are NFS 8 Underground 2 (damn bump steering...), NFS 12 Undercover, NFS 6 Hot Pursuit 2 and the more recent NFS 14 Hot Pursuit which had terrible arcade handling to the extreme. NFS 16 The Run took being bad to a whole new level though with set piece races and Quick-Time Events which were just shockingly bad for a dev studio trying to make a comeback (yes that's you Black Box...).
NFS World kinda skips inclusion as it's basically just Most Wanted, Carbon and Undercover taped together with some bad ideas for power ups and a lot of very tedious races with glitching opponents. Motor City Online is also skipped for two reasons, first it's not an NFS title (though considered one) and second it's not available at all any more due to lack of any servers.
Which brings me back to Most Wanted reboot by Criterion, the 17th NFS to grace the PC, hopefully the Burnout boys can bring something to the table that's less about rubber banding and power ups and more about the racing/running from the cops. The powers in their Hot Pursuit really detracted from hard racing as you were either about to get hit by one or hitting someone else with one. Meaning skill was dumped in favour of the random AI lottery of getting to the checkpoint first.
Personally I think adapting Shift 2's more realistic style with a slightly more arcade (forgiving handling) setup would give the best results, however SMS aren't on the case, it's Criterion...