C&C here also, especially red alert (1), allies vs soviets.
Or warcraft 2, also fun

Check out the game "Star Wars: Empire at War" (it's on steam). It has a surprisingly fun campaign. I'm still trying to get through single player mode, so I don't know if there is a skirmish mode yet.

I feel anything as old as WC2/RA, I'm going to be distracted by the dated nature of the graphics. I loved WC2 but pixellated 640x480 is an issue for me - I'm not after anything mind-blowing but crisp and able to run at highish resolution is nice.

I'll try Tiberian Sun since it's free and I never played it, but I fear it might not be quite modern enough. RA3 looks pretty nice and is apparently a 'proper' RA game, I'm currently looking at RA3 or C&C3 since C&C4 apparently broke the whole thing.

How do people feel about Supreme Commander? TA was a pretty seminal game although the scale of it was rather taxing for me... I wasn't gaming when SC or SC2 came out so have no idea what direction they went in.

Also - are there any online communities specialising in RTS I could join? I know not all game developers actually play games that much!

Rise of Nations, Tzar

Tiberian Sun has one of the best singleplayer campaigns even to this day. Graphically I think it holds up very well too, it certainly isn't an ugly game, and skirmish gameplay is good if you like building up your base, you can only produce out of one barracks/factory at a time so it doesn’t play quite as aggressive as newer games. My favorite of the newer ones would be C&C3 Kane’s Wrath, it’s a more modern take on the classic C&C formula (construction yards, tiberium harvesting, etc.) and the pacing and scale feel right, you get large armies but it still tends to be fairly fast paced.

Supreme Commander is good but I was never really into it especially in multiplayer, it has a different feel to a lot of other RTS, unit speeds and the way the economy is set up tends to lead to a bit too much spam.

As for communities, there’s gamereplays.org although that tends to have a multiplayer focus, maybe reddit/r/rts, and it’s worth checking out modDB.com, which isn’t a RTS community but there are a lot of good mods for various RTS games there.

How do people feel about Supreme Commander? TA was a pretty seminal game although the scale of it was rather taxing for me... I wasn't gaming when SC or SC2 came out so have no idea what direction they went in.

Also - are there any online communities specialising in RTS I could join? I know not all game developers actually play games that much!

I still play Supcom for at least 2-3 hours a week, on the "forged alliance forever" client.

Age of Empires was always good, a little more complex than the Blizzard/Westwood RTS's, IMO.

My favorite is always Medieval Total War 2, although I play with either the Stainless Steel or Third Age Total War (LOTR) mods, which are almost completely different games.

Tiberian Sun has one of the best singleplayer campaigns even to this day. Graphically I think it holds up very well too, it certainly isn't an ugly game, and skirmish gameplay is good

Cheers. I am having issues getting this to run - I downloaded it but it complains of missing DLLs, etc. I wondered if I need DosBox but trying to install that, some really weird things happened so I'm a bit concerned. Should it run on W7?

I downloaded demos of RA3 and SC2, after reading that SC2 was a bit of a scaled back version of SC. RA3 seemed quite nice but didn't grab me immediately. SC2 was exactly like playing TA but even in the tutorial, the sheer scale of the thing is pretty intimidating (just like TA). I think the distributed nature of the game is to 'blame'.

I really liked the idea that SC2 would use both monitors but the demo at least was rather flaky there. I'm wondering if my PC is a bit old for SC2 and might try the original SC game. Or C&C:TS if I can get the darn thing to work!

The version distributed from the EA/cnc website is patched to work on windows 7. If you go and buy cds online (I have the original cds somewhere too, they don't work) you will have problems due to its copy protection which was removed when they made it free, plus some other things. Works fine for me in win 7 64 bit. Just make sure you use the updater that comes with it to apply any new patches that have been made.

On this note you and I have something in common with rts games. I also prefer single player skirmish as I like to take my time playing and turtle the AI to death, e.g. Sandbag my way to their Base and build turrets on their back yard. Online players prefer to rush all the time and get games over with really fast, this isn't my style and it irks me...