I've also played all of the Civ games - except Beyond Earth - and I see Civ 5 like this. All the previous Civ games added more and more features and systems to the point where Civ4 either felt deep and complex, or bloated and weighed down by a bunch of crud that remained in the game because it had been in every previous iteration of the series.
Civ5 feels like a significant redesign and it's either more streamlined or, depending on your perspective, dumbed down. I like 5 quite a lot, although I think 4 is better. They're different enough that it's worth playing both, since you'll likely enjoy them equally for different reasons.
TLDR:
Get it. You're obviously a fan and will like it. It provides a different experience from Civ4.
