I know a few. For almost all of them i would say the stats are pretty accurate.
My sister has been going out with a footballer and the first thing I did was check his FM stats out - my sister then got excited about how much the game said he earnt (turned out he doesn't earn that much).
I was with a few pro clubs as a schoolboy then one year as an apprentice but this was in 1998 so I obvisley wasn't ever on any FM/CM game. Now a days with all the youth players on I probably would have been, which makes me gutted.
Being on an FM game would have been my greatest footballing achievement ever.