I don;t think i have ever played stronghold and it doesn't sound very good so i'll knock that one off.

Personally I have too go with Age of Mythologies which uses the basic premise of the age of empires series and simply adds a starcraft like asymetry to it.
I would of said Starcraft of course, but the things against it are thus:
It's a faster pace, which is not always the cup of tea for some.
Secondly it sadly comes in installments (expansion packs) and Age of Mythologies is actually better without titans; standing on it's own one might say.

It has the perfect balance of speed and strategy. It is not just about making a giant blob of high tier units, attack moving the enemy base and hoping your blob beats the enemy's blob (which is how most newer RTS games are played). Buildings are actually durable and have to be sieged, unlike most other RTS games (building durability, especially the defensive ones, is one of my main gripes in Age of Mythology). You can employ a vast variety of tactics and unit compositions. Resource gathering is an important aspect. Maps are not 100% symmetrical (a big one for me).

The setting being mostly medieval is also a big plus.

One game also worth mentioning is Star Wars Galactic Battlegrounds, which is basically a SW mod for AoE 2.

Company of Heroes and Warhammer 40.000: Dawn of War. Along with expansion packs.
They are so good I bough everything at release... even though I'm not avid strategy player and don't buy that much games at release.
These were exception (and Witcher 1 and TW2, along with Call of Duty: Modern Warfare when I got decent internet connection for multiplayer games).

Yes, they're more action oriented and surely catch attention even if you're not into this genre.

None of them. Given the choice it would be Powermonger (about time it was on GOG)

You are entitled to your opinion but i would really recommend checking out Stronghold even if you don't like how it sounds. You can get both Stronghold and Stronghold Crusader for less than 3 Australian dollars on sale. Stronghold Crusader has Overwhelmingly Positive reviews on Steam and 4.5/5 here. You can't go wrong with that. Worst case scenario you hate it, forgot to apply for a refund... And you have wasted 3 dollars, which is pocket change

I have never played Age of Mythologies on the other hand. I will check it out once i am in the mood

I play RTS games only for the single-player campaigns, I don't really care about skirmishes and even less about multiplayer.

Starcraft is still one of my favorite games, and the RTS game that I like the most to this day. I enjoyed Warcraft III as well, but only about the first two campaigns were very good, and couldn't really get into Warcraft I/II, so I never had the same attachment to it.

I like Stronghold, but I'd barely consider it part of the genre. IMO it is more of a real-time managerial/strategic hybrid, with even the option to play only the real-time managerial part.

Back in the day I loved C&C, especially the Red Alert series, and Empire Earth (that was a sort of 5 games in one), but then I enjoyed creating custom scenarioes with the editor, while now I have neither the patience nor the interest anymore.