Do you think he would've built the same empire as Michael did?

No. The overarching reason Vito always wanted Michael in the business was that he recognized (as Michael put it to Kay in New Hampshire) that his way of doing things was through. He knew the "olive oil business" had to transition to more modern, more "legitimate" businesses. He wasn't the man to do it. He was too old, too parochial, not wise in the ways of "legitimate" businesses outside NYC. He would have made a splendid consigliere to Michael had he lived longer, but he couldn't have led the transition without Michael.

Exactly TB. Vito did not have the global vision that Michael did.

I am not so sure he would have even made much of a consigliere once Michael moved into the legitimate" world, however it is interesting to speculate whether or not Vito would have sniffed out the hit in Tahoe before it happened. It would also be interesting to see how he handled Fredo's betrayal and Connie's shenanigans.