i dont really want to see anymore mythic dawn people
The Mythic Dawn aren't the only worshippers of Mehrunes Dagon, you know...
Yes, I'd say that Mehrunes Dagon should get a shrine in Skyrim, probably the reason why we didn't see a quest for him in Oblivion is because he is an antagonist in the main questline, and Bethesda decided it would be strange for the player to do a quest for the entity who is supposed to be your enemy. Skyrim has no such problem, and I see no reason Mehrunes Dagon shouldn't have a quest, though I do agree Mehrunes Razor seems a more appropriate reward, because it's more iconic of Mehrunes Dagon, since it's named after him. When I hear "Daedric Crescent", I just think of a generic Daedric weapon that happens to be crescent shaped. Not that I'd complain if the Daedric Crescent appeared in Skyrim, but if it does, I'd say it should be acquired through a different means, in Morrowind for example you could get it by using a unique amulet found in Tel Fyr, which would teleport you to an otherwise inaccessable Daedric Shrine where you'd fight a Dremora who uses it, and if you won, you'd return to the tower with the Daedric Crescent added to your inventory.