[Crazy Jetty]

They're nowhere near as bad as people like to trash them as being, so don't listen to that. Judge for yourself whether you like them or not. Pleasing yourself is all that's important, and no one else's opinions really matter.

However, if you only want them to be with your MU figures, the Infinite Heroes line are smaller than the MU figures. So not a good match. (Good match for TF Alternators, though!)
On the flip side, figures like Young Justice, and Justice League Unlimited are larger than MU. So also not a good match (Never mind the stylings are all wrong)
I don't really know about Green Lantern. I have a few, but no "normal" figures like Jordan or Sinestro. But at the very least, figures like Kilowog and Isamot are pretty good scale for MU.