In term of skills, you are probably right. It would take an unlimited amount of time to reach the best skills in Starcraft, "unlike" Donkey Kong. However, we also need to apply the "luck" factor, which I think is a big part of every game.
In term of skills, I agree with what you said Kyou-kun. But after, we need to know if the "luck" factor is part of being good at a game.
It's like the best Starcraft player in the world: We can't ultimately say that he's the best Starcraft player in the world, since luck/randomness always play a role in tournaments (like in every sports). Even if one guy is SO MUCH faster than everyone else, it doesn't mean he will win in a tournament.
In term of what can be accomplish, both Donkey Kong and Starcraft are the same, since there are no limit of the maximum. But in term of skills, ultimately, Starcraft has an "unlimited" progression of skills someone can have. Kindda like Donkey Kong, but DK has too much "luck factor" to take into consideration, maybe.
The best example would be Tetris: Someone can clear 40 lines in 20 seconds, but what would be the skill maximum of this game? If we say 15 seconds, then is 14,99 seconds not possible? Could we compare 14,99 seconds to clear 40 lines in Tetris to the best Starcraft player? And Tetris also has a huge amount of randomness.
It's sometime very hard to compare two "different" things. It's like comparing oranges and apples: you can agree that they are both fruits, but which one tastes the best?