I came into civving through civ3 vanilla so I'm a Civ3 fan (although i never did warm to C3C - just a preference, i like vanilla and PTW). I was also a fan of Civ4 BTS so I do like the grand diplomacy aspect of that game (which I wish could somehow be in civ3 & civ5).
I just finished my first few games of civ5 (w/G&K). I say it's somewhat similar to civ3 with regards to gameplay.
Although Civ5's diplomacy was a radical departure from the series, it actually plays a bit like Civ3's. AI with long memories of past deeds, unwilling/unable to compromise until utterly destroyed, no AI memory decay, unwilling to ally with a common foe because of something you did 100 turns ago.
The features I find really fun are:
- city states: not necessarily doing their quests but just as minor allies that I protect.
- intrigue and espionage (new to G&K). it's really fun and suspense-filled, i just wish I could get maps and troop movements. more spies and (stealing this from another civfanatic's idea) a news ticker telling me what's going on around the world whether that naval fleet my spy spotted actually launched an attack on another civ. although it could be vastly improved, it's already way better than civ3 or civ4 espionage.
- troop embarkment: it just makes things faster to launch a d-day invasion and general moving around. the problem is, the pathfinding in Civ5 is ok at best, awful at worse. Civ3 was no different but it doesn't involve embarking 3 different times just to get to a nearby place (each embarkment costs 1 movement point)
- different playstyles: Civ5 teaches warmongers (such as myself) to actually play peacefully and build tall empires so it's a nice change of pace to be taught new styles of play (never done either one in Civ3 or Civ4, throughout my Civ5 games I was constantly being dow'd on so I go and launch and a defensive force on their soil).
- Sprawling empire: Civ4 had to strike a balance of expansion and empire management, it's fun in its own way but I miss my sprawling empires from Civ3. That's somewhat back in Civ5 but the caveat is your social policies take forever to obtain. So I like my large-ass empire spanning a continent and half (manifest destiny!).
- Unique Abilities: UA is fun in its own right and is nice equalizer. Some are more useful than others but it's nice to see an AI civ turn tables on you not because of their unique unit, which can only be built at a certain era, but because they have an ability that counters your own even if they're massively outgunned (Japan's bushido is just a beast and G&K revamped some of these UA's to make more UA's useful).
- Religion: yes it's a little wonky at times but I like it's implementation as a natural progression rather than a force-place event (like Civ4) or the social policies were it's artificial and path laden. I just wish there were more religious wars (none happend in my games

)
Some complaints? some complaints...
1upt: A lot of people praise 1upt. I like it but only up to a certain extent. Traffic jams are sometimes atriocious and it's tough to set up with front line infantry and range support in the rear without your guys being blown to bits by the cities and whatever siege is garrisoned in it. The AI is struggling to use it but when they do get a nice trap sprung, it's devastating (i've been lured to that trap). But that's a rarity.
Social Policies: they are very situational and often passable since it's like techs but longer to get (and dependent on having a tall empire which unless I'm bottled up, I really don't care for). I think the depiction of a pink tech tree is an accurate one so that's a meh on that one. If they revamp this then yeah I might give it a nice nod as fun otherwise...
AI Embarkation and AI Invasion of other continents: The AI does not use embarkation to invade foreign lands or their neighbors, that has to change in the next expansion for sure.
Unhappiness. Never understood why unhappiness became the empire limiter. It should be health and or corruption not unhappiness. it's even stupidier when combined with global happiness so when you're succeeding on the front lines, your homeland is unhappy. why can't it be city specific then instead of global/local happy?
World wrap: I can't believe I miss something as simple as world wrap on map.
User Interface Information: this one i'm going to be schizo about. It's too much info and too little useful info.
I always thought Civ3 is the pinnacle of UI design because of its simplicity and elegance in displaying information. everything you needed to know at the city screen was there, all the spreadsheet stuff were neatly tucked away and you can visit at anytime. Also the info made sense, the advisors were sane and gave sane advise.
Civ5 although pared down than Civ4 still has too many spreadsheets and other crap you don't need. The advisors sometimes don't make sense or is giving wrong info. There's a crap ton of info that could be simplified and displayed in a better way. There's also a better way to display the diplomacy screen and all the other info. Civ3 already provided the template on how to do UI properly.
Conclusion: there's a lot of fun stuff in Civ5 but it's still a major work in progress to be as memorable as Civ3 to me