As someone who has played through all of them, I’ll chime in on MI2:
The basic ‘not mega monkey’ difficulty wasn’t that bad, it was fairly easy to follow, but the developers in the special edition of MI2 made it so that you had to run around every island to fully complete a puzzle.
MI3, for me, always felt a bit more polished (and Murray was always my favorite) vs. the earlier ones, while I preferred the ‘rougher’ look of Guy.brush in MI2.
Tales is really a spiritual successor, with the same world and characters, some of it was fairly hard, but otherwise quite worth the 1-2h per chapter. This of course after playing the Sam and Max sequels.
Having thrashed various versions of Monkey Island, I always preferred these over Sierra adventures for their forgiving nature. Monkey Island had better humor and the fact that taking a wrong turn didn’t kill you (Space Quest, anybody?).
There is a slight attention to detail that is quite fantastic, even going as far as the vultures that like to circle you on Monkey Island(tm). Some puzzles are stupidly difficult to figure out, at first, but that’s the way of an adventure game you can otherwise complete in 30 minutes if you ignore all the story and neat stuff hidden around (like skipping the guard in town in the last bit).
Overall Monkey Island, even as a series (not MI4, really), stands out as a benchmark of what point and click can be, as its best.