So what CM series game have you played? What are you getting into now?
Red Thunder is awesome because of the fact it has all the 3.0 updates, and is a great game on the Eastern Front.
Black Sea is also using the 3.0 engine, and I love it more because I prefer modern combat, (said it before, and I'll say it again... would really love a CM Cold War series based in the 80's.) but modern combat does have it's issues... mainly, even on the largest maps very hard to maneuver or fight close quarters... almost everything can be seen on the battlefield with drones, and very hard to get enough room to flank a force, without getting seen and shot at from a totally different unit across the map.
SO, IMO... if you love the series old or new, then the new WW2 games are great for you, only get the modern ones if your really into the full series.