I'd say either Reed or Tony Stark (For the whole brain aspect, though Reed's a better bet, since Tony likes to play hero. To Reed.)
Since Sentry is undefined, and with the possibility of him being high cosmic level, I won't count him (Or else I'd just say the Living Tribunal). So I'm going with the Silver Surfer. Lots of power, lots of wisdom, not rash for the most part, and with tons of experience to boot. (I said wisdom, but I mean wisdom as judging things and such.) Especially since he has some sort of undefined energy boost. But any energy boost above his non heralded level would make him that much stronger. I know I said I discounted Sentry for the cosmic reason. But if Sentry CAN go head to head with Galactus, that's puts him in a few leagues above the Surfer, who still can't compete with Galactus for the most part.
Doctor Strange, easily him. I'd say Shazam, but he could probably solve most problems all on his own. Not to say Superman can't, but Shazam would have WAY more dominion of ability to stop threats. Or maybe Doctor Fate. But Doctor Strange just feels more impressive.
