I would, cuz´ I said so.

:3

I fear Dr Manhattan erases Blue Marvel from Existence with his nigh omnipotent powers.

Dr.Manhattan would turn Blue marvel into a chicken then eat him

Doctor Manhattan blinks and Blue Marvel explodes, implodes and disintegrates all at once in every time-line, then gets reborn just so he can explode, implode and disintegrate again just to be reborn a third time - then Doctor Manhattan asks why Blue Marvel is bothering him and Blue Marvel goes home very confused..

Dr. Manhattan wins hands down. No contest. Blue Marvel is amazingly powerful in his own right, but the doctor is infinitely more powerful.

Also since I didn't give a reason why Doctor Manhattan would win, I'll just let the comics speak for themselves: