I am going to do a series of these, and explain what makes a good player in each of them, at every position. Starting with the quarterback, of course, the most important player in the game. Here is the breakdown of what's important:
Height: Taller QB's are in general better. I have played with guys anywhere from 6'0" to 6'5", and the 6'5" guys are easier to use in general. The extra height gives them less of a chance of tipped balls. This way you can stand in the pocket even when it is breaking down, and still make a decent throw with defenders all around you. You won't need to roll out with the big guy. On the other hand, a smaller QB is harder to tackle, so you can step up if there is a blitz, and avoid the sack. You have more freedom to move around.
Weight: No big effect. More weight gives player a stronger base, throws better while standing still. Takes more punishment with more weight w/o risking injury. If you like to run the guy, on a QB sneak, a guy who weighs 230 carries a load, and he'll pick up that one yard when you need it.
STR: More important than you may think. A higher STR rating allows your QB to throw better. When you have him standing still, the STR provides a base from which to throw, giving the throw more power and accuracy. Your QB will not be fatigued if he has high STR either, so you can run him around and he can take hits w/o getting too tired.
AGI: Good to move your QB around and make guys miss. YOu can buy time to throw the ball with higher AGI, and swerve and slink around behind the line of scrimmage.
SPD: Only necessary if you want an option style scrambler QB. Good when you are rolling out and running upfield for yardage.
ACC: Also good if you want to run him upfield. Other key is that higher ACC gets your QB dropping back faster. He is in position to throw quicker, therefore less sacks.
AWR: Only important for simming games. When you are playing the game, YOU are the QB's AWR. Make good decisions. With simming, the QB will play better if he is more aware. AWR 70 or better is a must if you are simming.
CTH: No real significance, unless the guy is a real Slash.
CAR: Surprise! This is important! If the QB has higher CAR, he is less likely to fumble while trying to throw. A guy with a low CAR may fumble when hit, or when trying to throw and being hit. With a low CAR, your QB is a risk to fumble whenever hit, so either protect him damn well, or make sure he's got a decent CAR rating!
THP: Determines how far and how hard a QB throws the ball. With a higher THP, you can really air it out for like 50 yard+ bombs. On shorter passes, you can really drill it in there, and put some zip on the ball. There is a disadvantage to high THP, though. On longer passes, a guy with high THP is likely to overthrow the WR by like 5-10 yards, regardless of his THA. Too much THP can be very aggravating in this manner.
THA: How accurate your QB can throw the ball. Precision is a must! A guy who puts the ball on a dime is ideal. With great THA, your QB will not overthrow the WR. Also, your WR's will not have to turn around to make the catch, slowing them down. They can get it in stride and keep running past the D, instead of turning around and being nailed, or falling down. THA is probably the most important rating during the game when you are playing with the guy.
KPW: No effect.
KAC: No effect.
BTK: Only needed if you are playing option-style, really, and running the QB a lot. Helps to keep him from being sacked on occasion.
TAK: No effect.
IMP: Well, if I thought this had any effect upon ANY position, I would tell you what it was...
PBK: No effect.
RBK: You wanna lead block with your QB? Be my guest. Kerry Collins does it, he's pretty good, too, at 6'5" and oh about 240.
INJ: Higher the INJ, less risk of your main man being knocked out of th big game. High INJ is good, then you know he'll be there when you need him most in crunch time, not being wrapped in the locker room, ala Chris Chandler (INJ 58). Get a guy with 70+ INJ.
That's all, folks. I'm open to people who want more analysis, who have any questions about the conclusions I have made, or people who disagree with these conclusions. I'll come with the post for HB sometime in the next several days, too, and FB. Hope this type of thing helps at all, tell me if it does. Thanx.