Really? because I can't think of any offhand. Sure there might be some cost associated with grabbing land so you can't just gobble it all up at once... but you pretty much want to grab everything you can at some point, and the reason you attack the enemy is to gobble up his land too.
Not so with civ 5. You want maybe 3 - 5 cities (depending on map size, etc) and you attack the enemy to kill him and burn down his cities because adding them to your empire makes you weaker, not stronger.
"Gobble up as much land as you can as fast as you can, within financial constraints for speed" sounds more like a wargame than an empire builder to me. Certainly it sounds like RTSs and a lot of military-focused TBSs I'm familiar with, with resource nodes replacing raw land in the RTS case.
I will admit, though, that my empire-building experience is mostly limited to the Civ games and more military-minded TBSs, like Warlock or Age of Wonders: Shadow Magic. I can't actually think of a proper, non-military empire builder outside the Civs and Alpha Centauri.
That said, if limiting empire size is a sign of being a wargame, I'm curious what not limiting empire size is a sign of. I'd associate it with RTSs, like Starcraft II, or more military-minded or at least less sophisticated and macro-balanced TBSs like Master of Magic or the Warlords series.
you attack the enemy to kill him and burn down his cities because adding them to your empire makes you weaker, not stronger.
Plus, this in particular. If attacking someone lets you gobble up his cities to strengthen your empire, it's obvious why you'd attack him- and it seems like combat is a major or at least very attractive part of that game. If it doesn't and the only point is to burn his stuff to the ground should you so choose... well, that sounds like a game where either the
whole point is to defeat everyone around you, or a game where attacking other players isn't the focus, and maybe not even a particularly good idea.