Valve built more games than Epic in the past 10 years. Epic essentially only released Robo Recall and Fortnite + extra content, plus a spinoff of Rocket League which was an acquisition. Valve released a couple of duds (Artifact, Dota Underlords) but also some good games: Half-Life: Alyx, Counter-Strike 2, and Deadlock. They also did "The Lab" and "Aperture Desk Job" which, while not full games, were quite good as demos for their hardware.