Doesn't have as many single player games as Playstation, sure. The Xbox wins in virtually every other genre.
Single player is a genre?
Let's do an honest comparison. Which games are the difference makers for each genre.
Racing - Forza, Forza Horizon, Gran Turismo, DriveClub, Wipeout. I believe most give this to Xbox.
Sports - MLB The Show, Everybody's Golf. I can't think of many other worthwhile exclusive sport franchises, so this would go PlayStation
Shooter (offline main focus) - Uncharted, Last of Us, Quantum Break, The Order, Killzone, Recore - PS4
Online Competitive Shooter - Drawn to Death, PUBG (for now at least), Halo, Titanfall (part 1) - Xbox
Action - God of War, inFamous, Gravity Rush, Yakuza, Bloodborne, DQ Heroes, Nioh, The Order, Gears of War, Sunset Overdrive - PS4 wins
Adventure - Until Dawn, Detroit Become Human, The Last Guardian, Shadow of the Colossus, Everybodys Gone to the Rapture, Ryse- PS4
JRPG - Persona 5, Dragon Quest (exclusive when just comparing PS and Xbox), DQ Builders, World of Final Fantasy, Nier Automata (for now at least), Atelier games, Tales of gIames, Disgaea, Ni No Kuni. Clearly PS4 dominates this category
Western RPG - Horizon Zero Dawn, Undertale, Dragon's Crown - PS4
3D Platformer - Lucky's Tale, Little Big Planet, Knack, Tearaway, Ratchet and Clank - PS4
2D Platformer - Cuphead, Ori and the Blind Forest, Odin Sphere, Salt and Sanctuary - Salt and Sanctuary is one of my favorite games of the generation, but both Cuphead and Ori are great, so advantage Xbox
Fighting - Killer Instinct, Street Fighter V, Dissidia Final Fantasy - SF is still a much bigger deal than KI, PS4
Twinstick Shooter - Resogun, Alienation - PS4
MMO - Final Fantasy XIV - PS4
That was quick and dirty off the top of my head. What did I miss?