Sentry's outfit is very similar to Superman's - and that's not surprising, given that he is one of many Superman analogues whose creation was influenced by the man of steel - but it is different colours (yellow and blue as opposed to blue and red) and it has the added bonus of not having a different coloured pair of underpants on the outside. Robert Reynolds supposedly possesses "the power of a million exploding suns" and what better way to represent that than a bright yellow suit (with sky blue cape) to go with his long blonde flowing hair. He may not be anywhere near as popular as Superman, but his costume is certainly an improvement on the Kryptonian hero's.
