Obviously the umbrella of 'procedurally generated' is wide and far, such as simple dungeon generation and randomized loot in a game like Diablo, to entirely simulated worlds of Dwarf Fortress to the sheer combinatoric madness of Binding Of Isaac.
People might say Nethack, I say Dungeon Crawl: Stone Soup because it's actually has a cohesive, thoughtful design instead of the complete mess that is Nethack. People saying Angband is the best are suffering from the rose-tinted glasses too; Angband is the slot-machine of roguelikes and there are better variants like Sil that remove the grind whilst keeping the excitement of what a new run can bring.
People might say Gungeon, but I'd say Isaac trumps it in replaybility because Isaac understands what replayability means, Gungeon is all surface. No-one gets as excited for a Gungeon run vs an Isaac run.
You might say Daggerfall, but what use is all that space and sheer volume of content when it's so empty and dead? Minecraft takes even more space but the game is designed in a way that all that space has meaning.
I love procedurally generated / aleatoric / generative game systems and I've played most of them and the problem that most of them face is the designers fail to understand that you can't just 'randomize all the things' or on the other hand 'have random elements' and expect either to work. The best games understand that procedural design and procedural experiences have to be crafted, developed, and designed. Spelunky understands this definitely.
But yea the correct answer is Football Manager don't @ me