Count me in too. I don't think I've ever posted to the Civ4 forum, but it still feels like coming home, from reading this thread. I think one of the few good things to come out of the Civ5 debacle is that it makes you appreciate what you've already got. Civ4BTS is, of course, the best - but I've also played a couple of games of Civ3 and CTP2 (both of which I used to play endlessly way back) as a reaction to the endless New Turn, New Turn, New Turn... ennui of Civ5. And both of those are miles more fun than Civ5.
And I really don't think that Civ5 graphics are better than Civ4's (as some have suggested) except on first sight maybe. If you look closely at the cities, they have no individuality, no individual buildings, just wonders if you have them. (The deep zoom is, probably deliberately, crippled out of the box, but you can fix that in the .ini file)
No fun with crazy aqueducts - look, someone was really trying hard to make that work in Civ4, and I appreciate their effort. (And workers don't seem to be having their way with cows and sheep any more. Where's the fun?) But for me one of the biggest graphics/UI things is that amazing zoom from Civ4 where with the turn of a mousewheel, you've gone right out from the centre of a city to the globe view from space. Gone now.
That stuff wouldn't matter so much, true, if there were some fascinating strategic depth to the game, but that's not there either. It falls on all fronts, every one. So glad I'm back with Civ4 and - as some others have said, looking forward to getting more into modded versions too - well I can't play it without Bug for a start, work of genius that.