I can easily see the difference between a 35mm negative enlarged to 8x10 and a MF or LF. At least, that's true if the 35mm is typical - shot hand held, with fairly fast film. Use a fine grain film like TMX or Delta 100 or Acros, lock the mirror up, and shoot off a tripod, IOW treat it like LF and the difference is a lot less but still there.
I'm much less certain of the difference between my medium format negs enlarged to 8x10 and my 4x5 negs. 11x14 starts to show up more, especially from 400 film, but the difference is still not stark. 16x20 really shows the advantage of 4x5, though medium format negatives printed 16x20 look excellent. 35mm...eh, depends on the subject as well as film, how it was shot etc. but it's a very rare 35mm negative that I'm personally happy with at that size.