I havn't played the new C&C, but I played through pretty much all the previous ones when they came out (Except Tiberian Sun..) So I'm basing the following comments on the previous games, but with improved graphics and aliens (lol).
TBH I think SUP-COM and TA-style games are simply superior to the C&C series. At the end of the day C&C doesnt actually have that much 'strategy' involved - granted you decide whether you're going to build tanks or planes, or both, but at the end of the day battles always come down to 10 or so heavy tanks breaking through and blowing up the enemy base. I'm not saying it isnt fun, but just that TA and now SC has a huge amount more depth to it.
Yes the games take a long time, and yes its CPU-intensive, but tbh I havnt got bored during a multiplayer game yet - even the 3hr ones!- and I thought it was worth upgrading my pc for!
Its down to tastes in the end. I can see how some people would find SC boring and long for quick battles with pretty explosions, but I prefer feeling like you've really earned your victory, when your clever strategy or just vast numbers pay off.