This was another big influence.
Simply put, d20 Modern took a set of rules I understood (Dungeons & Dragons 3rd Edition) and tweaked them heavily (classes, occupations, setting), and I loved it even more.
Maybe it was the idea of playing X-Files meets Buffy the Vampire Slayer, or the fact that the rules could more easily move to Wild West, World War, Pulp or Science Fiction settings than D&D could handle, but I really enjoyed playing and running this game.
I ran a lot of games based on the Agents of PSI setting from the book. Players work for a government agency investigating weird goings on. It’s all very psionics-focussed, which I tried to keep, along with cryptids and aliens.
It generally worked, but I wanted to PLAY an Urban Arcana game and never got to. That’s more like Shadowrun but less sci-fi hacker street samurai and more elves going to a rave.
I also stick Department 7 in as many games as it fits in. It’s a great little idea that really works well.
And yeah, the art style for most of the core books was fantastic.
I ended up with d20 Past and Future, the Dark Matter setting book (one of the better carry overs from Alternity), and some third party stuff too.
There’s plenty of stuff that doesn’t quite work, and that can be handled better by other games.
I wasn’t about to start playing Call of Cthulhu with these rules, or Star Wars, or Vampire the Masquerade (I’ve actually heard of someone starting a game of d20 Modern and it turning out to be a VtM in disguise – he lost friends over it who were sick of playing vampires and wanted to do something else!).
I also had a hard time selling it to people when I played it. In the meantime, plenty of other rulesets have appeared that make roleplaying in a modern setting work better – Fate, Cortex, and even Scion come to mind.