some more stuff:
felt more epic in civ2:
- building the spaceship (you could build various sizes of the ship, to affect capacity, speed, reliability and thus score)
- democracy/republic "civics" - big bonus, but you really had to "care" for them to keep them
- air combat - I never really got the taste for aircombat system which begin in civ3 and was followed to civ4
interesting, not necessarily better or worse:
- unit support system (unit supported from its home city by hammers, home city concept)
- caravan system
- war unhappyness - based on the home city concept, away units from that city makes citizens unhappy. (but could be abused via shakespeares theatre which does the same thing)
way better in civ 4:
- less grind
- due to no engineer transformation (aka terraforming), you have to work with the land you have, I like this. more variety in tile improvements
- AI, compared to civ4, civ2 feels like a sandbox game. AI was improved hugely in all aspects: combat, expansion etc. this might seem obvious, but is there as much improvement in AI from civ3 to civ5?
- diplomacy system , in civ2, AI sneak attacked any time one of its units met a weaker unit
- culture system, removal of troops before war.