Though I don't 100% agree, when my best friend and I talked about this a few months ago, I thought his opinion held some merit:
No. I don't need, or even really want, them to match me. However, I would like it if they tended to match each other. There is just something disconcerting about the fact that every game that has a group of protagonists always seems to have a team that looks like a rainbow. I don't need racial pandering, but I do like realism. It just seems unrealistic to me that if we built a team of the best good guys in the world, that every corner of the earth would be faithfully represented. Sometimes there are just some nations which don't have a ready-made superhero built for the job that is better than the second-best guy that one of the other nations could produce. I mean, if the Chinese had five guys who are all better than the best American for this mission, then unless we're bringing six members, I'm betting the American isn't going on this trip.
TL;DR: "Best in the world" =/= "Best from each nation" I'd like to see more of the first rather than the second. You know, the Olympic medal winners rather than simply the best participant from each team.