What game can make me feel powerful by leading an empire , army or fleet??
>>381027958
Mount and Blade is a start.
From The Depths is cool if you also like to design and tinker with the designs of your fleets themselves.
Children of a Dead Earth? Much more focused on designs instead of actually leading the fleet, though.
Cortex Command is a cute 2d, worms-like side-scroller, but it's more squad-based if anything.
XCOM?
That's what I can think of that I actually played.
>>381027958
X3:Albion Prelude with Litcube's Universe mod.
Check out some of its compatible mods and you can simulate military and/or economic takeover with space ships and space jewery.