Yeah, Civ4 remains the best. 5&6 are still good games, but and I do like that Firaxis tried to do things differently in many ways rather than just making a tweaked version of the previous game, but overall, neither is as enjoyable to play as 4. I also agree that the turn times are far too long on the more recent games, particularly 6. Even on a standard map with the default number of enemies, I get 20+ second AI turns in the late game, which is really boring to play, especially when your going for a culture or science victory where most of your turns take half that at best. God forbid I actually try to play on the larger maps. Sheer tedium.
As for what I've actually been playing recently, I picked up Slay the Spire a couple of days ago. I'm not usually a fan of Roguelikes, but I do really like deckbuilding games (though mainly tabletop rather than computer), a couple of friends recommend it to me and it was only £12, so I thought I'd give it a shot. And so far, it's been fun. The deckbuilding and combat mechanics are very well done, with a good variety of archetypes to build towards, and the relics you can pick up open up some other strategies. I suspect it's going to run into longevity issues for me, as there's nothing to the game beyond just redoing the semi-random series of fights over and over again, but given the cost, I'm pretty sure I'm going to get my money's worth. I'd really love a good story driven RPG campaign with the deckbuilding and combat from StS.