Yeah, I don't like Call of Duty, but it isn't because it is unbalanced. That would be a stupid reason to hate a game. (In some cases it is a reason to hate a game, but Call of Duty is not a game to hate because of this.)
Leveling systems are made to unbalance a game. That is a fact. What point does it serve, if it is not to make sure someone has an advantage? Even if the guns are perfectly balanced, the game is then unbalanced because some one isn't able to use a gun that would best suit their play style. Some one else will always have an advantage, because they have all the guns unlocked. Without the leveling system, it may be a perfectly balanced game, but because of the leveling system it isn't.
leveling systems serve the point of encouraging longer play time, just because someone is a higher level than you doesnt mean you will lose. also on the point of play style, what if someone unlocks all the guns and no gun fits there play style, can you blame a game on not catering to them and how they want to play? no. a perfect example of a game with levels that has virtually no rewards is halo. the level system in that game is pretty pointless and its still in, its in to encourage players to play longer, not to unlock better weapons so they can be better. multiplayer games in cod can be won without the need of going past level 1, and if you think someone has an unfair advantage, then your better suited playing private mode where everything is unlocked and you wont have to worry about anyone having a gun that you don't have.
as for your top games seeing as though none of them have any multiplayer, there is no point i can make from knowing about them. It would seem to me though that your likely one to avoid racing games and most multiplayer games all together as you would probably think them to be unbalanced.
How about the smash bros series do you enjoy that? because the only fighting game as unbalanced as the smash series would be the marvel series.