First game, second one or Shadow Magic? I loved the two later games, but the A.I is painfulyl thick. After a while in each level you get to the point where you know you're going to win, but you also know that it'll take another two hours to massacre all the A.I's free troops.
I actually really prefer the first one. Not quite sure what it is, as the latter two are better balanced and have much nicer graphics. But the AI in AoW1 is just not quite as stupid, and the campaigns are much better designed. The campaign in Shadow Magic is almost insultingly prefunctory. Consensus seems to be that Shadow Magic is much better as a multiplayer game. I've toyed with the idea of getting into some Play by email games but haven't yet got off my arse.
The first game's campaign is the most difficult. I don't know what they fed the AI in this game, but it's quite violent and the later games could have used that. Maybe there's scripted attacks involved? I'm not sure. This would be a good thing, but it seems to reward munchkin tricks (like starting your hero with Lightning Strike and using it to stunlock everything) over real strategy.
I purposely limit myself when designing my hero to avoid such cheese. Lightning strike and cold strike are particularly nasty, especially when combined with first strike and high attack and defence.
Then you have terrible boring levels no one should ever have to play like the two in the Dwarf campaign. AoW1 is also the most offensive in terms of "You're going to win. Keep playing this beaten level for the next few hours!" All that said, the challenge alone tempts me to try playing it again.
Actually, I found AoW2 and SM much worse in this respect. In Aow1, once it become obvious I'm going to win, I just make a beeline straight for the enemy leader and that's the end of that. Not so easy to do in the other games.
Age of Wonders II has some laughably uneven difficulty. The first campaign level is much more difficult than most others. I only played one that was more difficult. The rest consisted of "build up stack of doom, steamroll everything". Levels are also generally less interesting than in AoW:SW. Does this get more fun in the second half of the campaign?
The Aow2 campaigh was bad. As far as I can recall, it doesn't get any better.
Age of Wonders: Shadow Magic is the only game with real unit balance thanks to a fan patch you can download. This is the only game I would consider playing scenarios or multiplayer because of that.
I really need to check out this patch, if I don't OD on AoW1, anyhow.
Hated the shadow demons and their alternate dimension tileset. I played 'til one of the nomad levels where the AI ignored me the whole game, sat around waited for me to build up and kill it. Maybe this game deserves a second chance.
I wasn't a fan of the two new races or environments either. The passive AI was infuriating. But as I said, I've heard it's better in multiplayer.