Skids, an old New Mutants character gave up adventuring and went to college and lives a normal life.
Reminds me of an old Playboy cartoon of a bunch of costumed individuals in a room – some watching TV, playing checkers or otherwise amusing themselves – except for one who is saying something like, “Hey guys, why don’t we go outside and fight crime!”
“Skip” Collins from Fantastic Four 234, aka “the man with the power.” He could bend reality to his wishes, but was so unassuming that he didn’t even realize he had the power – and probably wouldn’t have wanted to do anything dramatic with it anyway.
Yeah, but Hundred hung up his cape once he realised he was “at best, maintaining the status quo” and, at worst, endangering people. He thinks he can do more good in office than in tights (debateable, as the 9/11 attack [which he stopped], the crazy snowplow-killer and the weird alien woman all came after he became mayor).
IIRC, stopping the plane on 9/11 happened before he ran for Mayor – and was, in fact, a big part of the reason why he was able to get elected.
Wonderman, from “TVFunhouse” mostly used his superpowers to get his alter-ego laid. Sounds perfectly reasonable to me.
As I recall, he was halfway through his mayoral campaign, and doing abysmally, when he stopped the plane. But he’d definitely hung up his tights.
So we were both wrong. 
Then there’s The Watcher, who mostly just… watched.
Oh, you shall rue this day!
Well…start rueing!
I’m not sure if Mr. F.G. Superman counts, after all, he’s no different from any ordinary Superman…
then of course, there is always Bicycle Repair Man!
I don’t think the Incredibles count. They would have certainly been actively hero-ing if not for the government order that shut down all super-activity.
Zenith a selfish and rather cowardly teenager who uses his powers mainly to advance his career as a pop singer.