GC 1 is little more 'tactic'; almost always you don't need to rush and can think about next moves. GC 2 is for sure faster, less time to think about tactics (but it's still important), quite simillar to World in Conflict. In GC 1 you have campaign, also there is possibility to playthrough missions from campaign seperate as single missions. GC 2 has campaign, single missions, skirmish, custom maps.
. GC 2 isn't worse from GC 1. It's just different. All depends from play style you like. For summary I advice anyway to start from buying GC 1. Story from game is awasome.

I didn't like the single unit control that GC2 decided on. The squads in GC1 were far more efficient.
I just think GC2 tried to go back to traditional RTS, losing a lot of that unique aspects that GC had. Still, worth playing both.

I've not played GC2, but I have played GC1 and I can confirm that yes it does have skirmish play.

I've played GC2 with pleasure.
It felt a bit weird at the beginning using single units but this is way easier to make squads when defending crossroads. Anywayz , ik really liked GC2 , it looked nice , had a great story but i still prefer GC1.
So if you're not sure , buy it from here as you won't find it any cheaper somewhere else.
Give it a try , you won't be disappointed
IN GC2 there's a few scripted events : like 1 where you have to run from a really big army barely escaping , 1 where you get hammered upon arrival having 30seconds to organize yourself, ... . Feels great when the mission is finished succesfully :p