Okay well, here is a guide for everyone:
For Key Defenders (FB, CHB): Basically the most important thing is how your opponent went. If their FF or CHF (depending on your own position) kicked more than 3 goals, you have been beaten, unless they only got 4 kicks for 4 goals. Your marks are quite important too in this position, so if you got more than 5 you did alright.
For other defenders (B, HB): Your opponent is still important, but so are your posessions:
< 10 posessions: Only alright if your opponent was worse.
11-20 posessions: Serviceable game
> 20: Very good for a back pocket and good for a half back.
For a midfielder (Wing, Centre, Ruck/Rover, Rover):
< 10 disposals: poor
11-20 disposals: average
20-25: good
26 + is very good, 30 is the benchmark for ball winners.
Goals also help you out, as do tackles.
For small forwards (FP, HF): Posessions and goals are your most important stat (tackles and marks are also useful). If you score 3 goals or more, you have probably done your job, unless you missed a few as well.
Key Forwards (CHF, FF): Your marks and goals are very important. As the main target in the forward line, you need to consistently score goals to make an impact, as your posessions at ground may be limited.
0 goals: poor
1-2 goals: average
3-5 goals: good game
6+: great game
Ruckmen need to get more hitouts than their opponent, and can also take marks and kick goals from time to time.