Supreme Commander

the plot is average in the supremme comander 1 or FA. where this game shines is it's battles in the skirmish mode!
however if you have time then play through supcom 1 campaign then move for FA.
in a nutshell FA gives a new faction and more units to make new battle strategies.

Hm I'm just interested in skirmish mode. So I'll just move on to FA then.

Thank you :)

SupCom 1 then SupComFa and last SupCom 2 if you want to folow the story.

I agree with these gentlemen, first play SUPCOM and then play FA.
And please note: SUPCOM is one of the most fantastic games ever made IMHO, but SUPCOM 1 and FA have one flaw: they don't use multi-core CPUs well, so large battlefields tend to lower the game's speed. This doesn't happen in game's campaign, so I think campaign is better than skirmish in that game. Enjoy it. :)