Michaela - It sort of sounds like you are saying if he learns how to follow the game rules and take turns with a parent then he will be able to play with older kids successfully. In my experience that's not how it really works. Most preschool and lower elementary kids don't play board games successfully with other kids. It tends to be an activity they do more with older siblings or adults. Even if your kid gets it down 100% with you he still may not find 4-8 year olds who are able to do the same. Many in this age range will creatively change the rules as it suits them and your son who has been taught to follow the rules may find himself totally unprepared to deal with that. And, none of that is getting into the reality that five year olds may have no interest in playing with a two year old no matter how advanced.
That isn't to say you shouldn't play card or board games. They are lots of fun. It may also be an area where he could start to learn to play by himself (or against a teddy bear).
I agree with this. My daughter is 28 months old, and she tells me on the way to the park that she hopes there aren't other kids there. She is very shy, and other kids will take advantage. They wont wait for their turn. They push her out of the way, and it makes her feel terrible. She plays Candyland and Hi-Ho Cherry-O at home. She takes turns with me, her mom, and any dolls or stuffed animals in the area.
We recently brought her on a trip, and exposed her to more 2 year olds. She's gotten to the point that when someone wont share, she doesn't fight at all to keep a toy she's been playing with. She just lets them have it with a disappointed sigh, and goes to get something else.
It seems to me that sharing and turn-taking are atypical behavior for this age group, and highlighting the fact that the typical toddler is deficient in those areas wont necessarily make it easier for your toddler to get along with their peers. On the other hand, if there are older cousins around they would probably be inclined to play with your son, especially if he plays by the rules.