A game that is not for beginners but is absolutely awesome for strategic gamers is Dune (1979). Up to 6 players and is best with 5 or 6 players - great theme, amazing gameplay and is balanced despite being asymmetrical. Has area control, card management, card auctions, a great combat system, alliances with different rules, this thing has it all. Decades ahead of its time in terms of mechanics. It will take 2-4 hours to play.
Dune is a great game - one of my favourites.
It's been out of print for decades. Fantasy Flight recently re-themed the game into the Twilight Imperium universe (they couldn't or wouldn't use the Dune IP). It's called "Rex".