Funny, but all of the ones I've played except MSHAG have workable playable stats for cosmic level Supers.
MSH/RMSH/AMSH, Marvel Heroic, Marvel Super Heroes Adventure Game, DC Heroes, Champions, Champions New Millenium, V&V, and Sentinel Comics. (I have, but haven't used, GURPS: Supers)
The thing is, in almost all of them, it's not a random gen starting PC level. (It is "rating them from the books" buildable in all.)
Both GURPS and Hero have the ability to build and run demi-gods as PCs... as evidenced by Hero/RM Mythic Greece, and by GURPS Lensmen. Insane point levels.
V&V is quite random, but I saw a PC that felt Supes level.
MSH/RMSH/AMSH — Only buildable by the rating an existing character method.
MSHAG: no. Not meaningfully.
DCH: clearly, it includes Supes himself.
MHRP: it pushes the scale just a bit, but so does Galactus.
Champions and CNM: Doable, not even too high a point total; credible at 500 points; non-optimized, around 1000. Every power ever used? maybe 2000. Full on Greek Gods are 3000-5000.