That is tough because usually tier lists are based on whether a character has bad match-ups or not, particularly against other popular characters. A lot of the 'average' cast members have some problems with some match-ups, often against Superman or Black Adam. I'd say the 'average' character has issues with one or both of these two, or one of the other top tiers. From what I've seen, a character who had nothing but 5-5 match-ups would be considered 'better' than a character who has 20 match-ups that are 7-3, but 4 match-ups that are 3-7, particularly if they are 3-7 against someone like Batman who is bound to be in a tournament.
If in my low-level player estimation I had to pick one, I might suggest Green Arrow. Chris G has shown that Green Arrow can handle pretty much any character in the roster, although this is usually attributed to Chris G being a phenomenal player, not because Green Arrow is particularly special. He seems to be able to hold his own against just about anyone without necessarily being a dominant force either. Heck, the archer can handle Doomsday's rushdown, that is saying something. In spite of Chris G doing well consistently with Green Arrow, Green Arrow is not considered even a top 10 character AFAIK. I don't think anyone else is maining him at the high levels. No one playing Green Arrow is accused of tier-whoring, that is for sure. Another benefit is that there is a lot of source material to watch on how to play him, namely Chris G tournament videos. My $.02.
