Hard to say because IV is waaay better than the rest of the series IMO, which is not saying anything bad about the series because I'd play any of the games any day. If you want something like IV, get Etrian Odyssey Untold: Millenium Girl. Play it on Classic mode. If you want something really off-beat, Etrian Odyssey III is great (but you have to get a physical copy). The classes, the sailing system, some of the areas and enemies are just so weird. Half of the classes seem super original in a way where it's not necessarily good or bad... just weird.
EOU on the other hand is pretty straight-up and simple, which I like.
If you play EOU on Classic, make sure you go into the options and switch to the modern music settings.