Heroes III is seriously one of the best games ever... it's about 8 years since I first played it and I'm still not bored of it. I've had some great Heroes II/III hotseat sessions. I've always been biased towards the spellcasting characters because Town Portal is pretty much essential for large maps. I never really got into IV/V.
Have you guys played the Might & Magic RPG series which was an offshoot of Heroes? MMVII and VIII were sick games (especially the first). Both feature the minigame
Arcomage which in itself is fun. I never completed them when I first played so I went back to them last year and finished both.
C&C3 was good too - I've played through the GDI and Nod campaigns but never got around to doing Scrin. I get a bit annoyed with multiplayer though because it's hard to tweak it just right so that you can get a game which is consistently difficult throughout its duration. Either, it's far too easy, far too hard or it's a challenge for a little while after which you can steamroll your opponents.
I didn't really like the sound of the radical changes made in C&C4 but I've yet to play it, so perhaps I'm in for a pleasant surprise?
Btw, if you any of you want to laugh at the archaic graphics of MM7, here are some vids. Only the second one has any combat.