Stellaris is certainly one of the best PC strategy games around, allowing you to fully customize your faction and wider game experience. It's a true sci-fi epic that offers mountains of replay value. However, when it comes to determining the "best" PC strategy game, it's important to account for taste and personal preference.
Despite its strengths, a die-hard fantasy fan may well get more from Total War: Warhammer 3 than the likes of XCOM 2 or Stellaris. In the same way, those who want an experience more grounded in the real world are unlikely to find a better title to suit their tastes than Civilization 6.