My guess as well prior to entering thread. Might be Michael Spinks and even Qawi of 1st Holyfield fight. Maybe younger prime versions of Adamek or Cunningham or Guillermo Jones. 1994 Foreman was a dead man walking.
We'll to be fair, if Tommy Morrison can stick to a game plan and stink out a victory, there's quite a few names that at least "could" defeat Foreman. Jones Jr might not be a bad shout either, he'd obviously have to avoid taking anymore than minimal punishment though.
It's funny. The only way I can envisage Foreman winning against a lot of the names mentioned would be in similar fashion to the way he beat Moorer. I'd never feel comfortable backing a fighter to win in the likely hood of a one punch knockout, but Big George could still bang even in the 90s.