I've played since Civilization I.
Civ I was incredible for its era.
-did I really just lose a tank, a bomber, and a battleship to a spearman???
Civ II increased the scope beyond anything before.
-The custom palace.
-the advisors
-the new government types
-espionage
-civil wars!
-terraforming!
Civ II: Test of Time
-It was epic in scale, all of a sudden you actually landed on Alpha Centauri, and there is already hostile life there!
-Midgar scenario, sort of a pre-Fall From Heaven II, you can live underground, on land, in the sky with mountain tops as "islands", or under water.
-The 4 layer solar system one, yes you can colonize the upper atmosphere of a gas giant.
Civilization III:
-added national resources, this completely was the biggest upgrade the game had.
-the scenario's were incredible
-I hated whack a mole pollution, it made corruption seem okay...
-artillery was awesome, especially defensive bombardments!
-air bombing was awesome too, stealth bombers even more cool for some one sided wars, research enough tech and you even get precision bombing
-enemy nations change appearance based on era!!!!!
-Armies from great leaders or building from the cities with generals. If you have trouble with overly hardened cities, just move that army over there!
-Rise of Rome, enough said.
-stack of doom, mean my fleet of bombers!!!
Alpha Centauri:
-Custom Units, that's right Beyond Earth, I get to design my own stuff.
-unlimited terraforming, that's right it actually makes a big difference.
-humidity
-elevation
-aoe bonus's to adjacent tiles
-forests
-fungus production
...ummm it can get a little tedious
-AI factions are kinda neat, and the storyline is incredible, don't forget the expansion
-Dead IP, they don't own it, so it isn't going to be redone anytime soon.
Civ IV: Vanilla
-I can't build trees/forests anymore?
-the terrain was extreme especially when you start to really get into the techs, I like how I can't just play Egypt/Native American's and irrigate the whole Sahara Desert anymore. It made colonizing jungle areas really feel like you are doing something.
-unique faction buildings are incredibly lame, seriously Egypt gets a special monument that you can't build in like 20-30 turns.
-bombardment was illogical, the point of artillery is to sit back and bombard, not go charging into a city, I don't care what anyone says. It made stacks of doom worse as well, because now you artillery DIES when they attack.
-air units were kind of weak and odd. I mean yeah you can steamroll with them and tanks, but they didn't feel very well implemented.
-Modding, I seriously have spent more time playing Civ IV than any other video game ever. Modding just makes me play more.
Civ IV: Warlords
-Warlords aren't really that interesting, wow some extra XP on that now dead unit, I'd rather use Genghis as a trainer in a production city.
-Vassals, kinda neat
-Scenario's well they aren't that interesting....
Civ IV: BTS
-Scenario's were super neat!
-finally a fully fleshed out game
-it still crashes all the time
-espionage is still lame
-I don't care this game feels like a continued sequential extension to Civilization I
Civ V: Vanilla
-Wow, this is a lot like playing on my XBox
-Despite me not liking it, I can't really suggest people switch from V to IV if their first game was Civ V in the series.
Civ V: XCom??? (oh nevermind sorry) the apology expansion (whatever it was called
-well I have to admit it is comparable in depth to Civ IV with the expansions now. The only problem was it took you WAY to long to get there, stop streamlining and instead make a full game.
-yeah religion blah blah blah we all know they added a ton of stuff into the game
-Why does this 1UPT thing make it so that when I try to move my units to attack the other guys it is more tedious than back in the old days, yeah sure run off the damn railroad track, make me micromanage MORE
Civ VI: An incremental change, (not upgrade) to Civ V. Which is probably a good thing, too much change and people get pissed.
Overall I've literally seen all of these new features in dozens of other games. It is starting to look like Rome: Total War meets Warlock, with Civ 5 graphics.