[allthesethings]

Civ Revolution is the "streamlined" version of the game for consoles. It's a good introduction to the series as a whole and a joy to play in shorter sessions. (I haven't tried its followup)

Of the mainline series, 1-4 is a straightforward progression that doesn't rock the boat too much. Civ1 is still fairly easy to get into but has a lot of crude, unbalanced or easily exploitable elements(e.g. the AI has a random chance of building a Wonder of the World every turn instead of having to actually allocate a city's production to the project over many turns like the player). Civ2 has fewer exploits and more polished 90's-era graphics, but now the number of units and cities explodes into a very tedious, micromanagement heavy late game - the degenerate strategy of Civ2 is called "smallpox" because it involves spamming a lot of small cities across the map. Civ3 added a lot of additional balancing and finetuning and graphical flair, and Civ4 does more-or-less the same. I have trouble remembering Civ3 after Civ4, really. But the basic feeling remains consistent: Most Civ strategy is focused around optimizing fine details across your entire empire towards a focused direction, so that you survive now and gradually get ahead of the AI players later. And the late game slows down because a lot more is going on in each turn. It gets hard to keep track of things.

The games after that make more drastic changes. They still feel like Civilization, but with major changes to the cities, board and combat components that differ from the "Empire" model that had been employed since the first game. The ways in which you have to make tradeoffs of "now" versus "later" or the kinds of capabilities to emphasize are more varied. And they have higher system requirements - Civ5 at release was quite heavyweight and buggy, and Civ6 has gone similarly. But these are things that everyone expects will get smoothed out with time. With the newer Civ games, it's more a case of the designs just being different versus being definitely better, with emphasis placed on different things.