RTS recommendation

[Slimebeast]

Easily Age of Empires. Especially AoE II - The Age of Kings with The Conquerers expansion.

But if you want 3d graphics you will choose Age of Empires III.

Third hand choice is Mediebal Total War.

Mount & Blade is good too, ppl who like RTS like Mount & Blade too because it's an RTS-Sim kind of.