Yeah Most Wanted is a bit iffy. I've played it through on PS3 and Vita and while I'm not the game's biggest fan, I will say it's alright once you get used to it. I don't like the teleporting between cars, having an open world with so many stupid collectibles, the way you find the cars rather than unlocking them etc.
I'm about half way through Rivals, I'm at around 55 races gold (100 required out of 136 I believe?), but I'm only level 21 (cop) and 18 (racer) out of 60 required for both factions (Talking solely about unlocking the here, technically I'm done with the cop career, the credits played and everything! ) My only complaints about Rivals is: How you can't pause mid race or at any point really, and how the game feels like you're just checking off a list. Rather than unlocking and winning races... Good game though.
Hot Pursuit is easily my favourite though, once you're used to the heavy handling of the cars and the rubber banding AI it's really good fun.