A champion whose level of skill at an activity is so much above that of the common mortal, that mortals aren't really any
competition for him. They might as well be facing god, because they're
never going to win a single bout.
The term started being popularized by the game Unreal Tournament where the voice of the announcer shouts: GODLIKE! For all to listen, when a player kills 25 enemy players in a row, without dying. This feature was later added to other popular games, DotA-like games being of the most prominent.
Interesting Fact: In DotA you only have to kill 10 players in a row to get Godlike'd. If you kill more than 10 in a row, the DotA announcer says: HOLY SHIT! and adds a subtitle: 'Player is beyond Godlike. PLEASE, somebody kill him!'.