What are the best pure tactical strategy games for you ?

Arma 3 or CSGO

Total War Shogun 2 seems to be just the thing. Doesn't get any larger than that.

Supreme Commander? Heard 2 is kind of weaker than the first one.

Ruse is -75% right now also.

door kickers / swat 4 (no steam) / rainbow six 3 raven shield / full spectrum warrior / company of heroes

Incubation: Time Is Running Out

Have you been looking into the Dawn of War Franchise? The unit count might be quite low (lower than WC3 even), but it's much faster paced.
And it's pretty obvious: StarCraft II

Europa Universalis IV (CoP, RR, WoN, AoW. Are all good dlcs to buy)
Total War: Rome II or Shogun II
Sid Meiers' Civilizarion 5 (not Beyond Earth)

Command and Conquer series? or Stronghold perhaps?

I'm not all that sure what would be defined as a "pure tactical strategy" game. It sounds like you're looking for games closer towards an RTS play style, though, and I don't play many of those.

• Sins of a Solar Empire: Rebellion is pretty good. It does have a bunch of research stuff, though, and there's not really anything in the way of terrain/obstacles.
• WarGame could be worth checking out. Personally, I just couldn't get into the game. I don't even know why, haha.

Even though they're probably not quite what you're asking for, these games are really awesome, and I highly recommend checking 'em out:

• Silent Storm
• Nexus
• Star Wolves
• XCOM: Enemy Unkown
• Jagged Alliance 2

Here is a list of games on Steam with the tactical tag. It might be helpful.

try prison architect... it's different but you might enjoy it

Dawn of War I & its expansions is a personal favorite of mine.

Also, because I doubt anyone else will mention it, The Lord of the Rings, The Battle for Middle-Earth II is worth a look.

(Based on your question, I'm assuming you want an RTS, and not a TBS or 4X game)

Action strategy games then.. Try Supcom (2 is fluffier, 1 is the better game);

• http://store.steampowered.com/app/9350/
• http://store.steampowered.com/app/40100/

If you decide to go for 4x-lite in space, SoSE: Rebellion is good but shines with the DLCs:

• http://store.steampowered.com/app/204880/

Saw you found Civilization as too complex, so avoid anything by Paradox and Grand Strategy and most 4x in general to be fair..