I just voted that Civ 2 is better than Civ 4. But I should say that it MAY be better than Civ 4, if properly customized, in my view. Heres why:
-First of all, Civ 2 is the most easily modded game Ive ever seen. Which makes it easy to adapt to anyones particular taste.
-Secondly, because of this factor its easy to address the main issue: that its easy to win once youre experienced, even at deity level. There are many ways to go about this, and I dont think that is the case with Civ 4, which is more limited in this sense.
-Specifically, one way to make it awfully difficult to win is to add one hugely expensive, highly powerful, highly desirable unit or two. Since the AI will always create the best available unit, with little concern for cost (everything is cheaper for the AI), they can have hordes of say, very fast, powerful cavalry attacking your empire in mid-game, or very strong, super-destructive bombers for late-game situations. Of course, the human player can also build these units but, given that the AI advantage in building costs, this is a definite AI boost. Effectively, you can make the game as hard for you as you want. I dont think you can do this in Civ 4.
-Another way: use the cheat menu at the very start. I recently did a test, in which I put every single ruler (playing 7 civs) against me, by clicking on the revenge square. I was lucky in the initial setup of this game, and later during gameplay, so it looks as if Im going to win as of 1930 (but I also have super-bombers set up in this game, that havent appeared yet). If I still win this one, my next test will be to have every AI ruler at 90% hostility against me (or higher). Which is sort of simulating what happens when you play against humans
I havent played Civ 4 that much (I uninstalled the game years ago) but, again, I dont think you can turn the AI there into vicious competitors, at least without some more complicated tweaking.
-Beyond the issue of how hard it is to win, there are other advantages to Civ 2. One is simplicity: its just easier to keep track of everything thats going on, and focus on the hard choices of strategy, beyond tactics. Civ 4 is more comprehensive, has more info all over the place, and more choices, which is good, but takes up more time to ponder the implications of any big move, like declaring war, or devoting resources to such and such region, as opposed to another. Another issue is the absence of the feel-good stuff, like the possibility of achieving victory by cultural superiority. Even if it made any sense (which it doesnt), I personally find it boring to win a game that way.
-Colonialism. Since Civ 3, colonizing enterprises are awfully difficult. Its possible to go out and found far-flung colonies, but it is much harder. And the AI in Civ 3 and Civ 4 expands fast, covering the entire map soon. In Civ 2, playing in the largest map, theres always empty land at any point in the game so, if you want to, you can start new colonies from scratch even in the 20th century. This is more fun, as it always gives you an incentive to spread your units around, and is also more realistic. Historically speaking, colonization wasnt as hard as it is in Civ 3 and Civ 4. For example, a bunch of Spaniards took over most of the Americas with relatively little fighting, because of significant tech superiority and the effect of their viruses on the local population. By leaving lots of space empty, Civ 2 addresses this reality better (without the need for actual killer viruses).
Anyway, just my view. Both are great games really; and maybe recent modding of Civ 4 has made it more to my liking.
