I'm looking forward to this game as much as anyone, but i have my reservations too. The original Westwood team that made C&C and was responsible for the wonderful atmosphere of the game have all been relocated to other projects (The Sims is one of them), whether the current team will be able to match their predecessor's awesome work is still to be seen.
Also, the engine may be the same, but it can still have been improved, just like the game looks a whole lot better than Generals/ZH.
Generals is a bit of an oddball anyway, it's got the name of Command & Conquer, but takes place outside of the regular C&C universe. It's not a bad game by any means, the contrary, but shouldn't it just have been called Red Alert 3?