Well i have used Unity the free version and its brilliant for a free version but C & C2 are completely different products aiming at a very different market of game developers.
I have also used Game Maker and Multimedia fusion which both have their own praises, but the Cost of MMF 2 is ridiculous for the CASUAL game maker like me who loves messing around and just enjoys creating bits and bobs here and there, But C2 will also have great appeal to more serious game makers out there. This is where i believe the pricing for this product is the BEST i have ever seen.
I own alot of game making software from DBPRO to FPS Creator as i'm a game making tool junkie.
So back to Flash, Java, WEBGL and god knows how many others oh Silverlight, Adobe Air any other to compair to... Oh yeh Game Maker... MMF2, Unity, Blitz Basic and 3D, Oh Torque 2D and 3D.. what i'm saying is it don't really matter, HTML5 is new and will probably be around for another 10 years getting better as it goes along, And Gaming online in web pages is getting BIGGER and BIGGER every minute so thanks Scirra for this dam fine product, i'm glad i got in at the beginning and am excited at the future for this product.
Wether you add EXE,FLASH,JAVA or what ever else you add as long as it does what it says it does, and makes games to play on web browsers i don't care whats going on behind the code whatever language it uses, i want simple point and click to create games and this does that.
BRILLANT is all i can say...
phew rant over :)
Also places like Facebook have made 2D web Browser games quite popular..