I've used Kodak Max 400 in my Pen EES-2 (very similar to your EE-2, probably the same Zuiko 30/2.8 lens) and been pretty happy with it for small prints. In fact, I used ASA 400 color print film in this camera twenty years ago and liked it then, for small prints.

And small prints are really the norm for the 18x24 frame in any case. Yes, you can enlarge; they make good 5x7 and pretty decent 8x10 if everything is just right -- but there's no substitute for negative area (to paraphrase the old drag racer's creed). Pretty much any of the Kodak ISO 200 or ISO 400 consumer films should work nicely. If you like B&W, you can probably get pretty big prints from T-Max 100 (though it's not much more tolerant of haphazard exposure than slide films), Delta 100, or even from traditional medium speed films like Plus-X, Fomapan 100, or FP4+, and you might want to try a roll of XP-2 Super or one of the Kodak C-41 B&W films.

The problem you'll always have with C-41 in that camera, of course, is that although any mini-lab can process the film, almost none of them can/will print the half-frame correctly; you'll get 2 frames per print and compromise exposures. At least with B&W, you can mask your negative holder and print just a single frame. In that respect, XP-2 Super may be the best C-41; its clear base is intended for printing in a traditional silver-print darkroom, and you can get "negatives only" for $2 to $4 at any one-hour lab.