This question does come up every now and again. Previous thread on the same question here

The TL;DR of it is that

It's possible to come up with hypotheticals about how Germany could have won, but all of them involve a chain of ludicrously improbable events to have occurred, or the simple hand-waving away of enemy armed services or belligerent nations in their entirety.

I think this is more question for /r/HistoryWhatIf than here since this question require speculation.

In short. Whole World: No. Big Chunk of it? Yes. Especial if they were little more reasonable. (Less relying on vunderwafe, less Politics in military decisions)