For me, it really depends on the game and the setting. I have run supers games, and I'm currently running a Naruto-ish ninjas game (but I repeat myself), and in games like those I'm fine with, and indeed want, the characters to regularly be performing superhuman feats. I'm also currently running a Call of Cthulhu game - where the characters are decidedly very much human, and I would not be happy if they were performing at more than what we all determined was a proper level for people who were competent professionals in their respective fields. Somewhere between is the Shadowrun game I'll be starting soon - yes there's magic, yes there's people who have bodies enhanced by magic or cybernetics - but I wouldn't be expecting them to perform like the ninjas in the first game, even as they consistently outperform the "normal men and women" from my Call of Cthulhu game.
Which is all a preamble to my answer as it pertains to D&D - it depends on the campaign that I'm interested in running and my players are interested in. I've run games that we all agree will have a maximum level of 6, I've run a lot of games that just come to a natural conclusion somewhere between 8-10th level, and recently we ran a game to 12th level. It's been a long time since I've run a game that went higher than that - so empirically, I can say that in D&D we prefer our games to top out at 12th level. But in our games, we don't generally aim for a specific max level.