Yeah, GURPS is one of the best plug & play systems ever. Sometimes it was a bit ponderous, simply because you can do so much stuff.

As far as what I like, mechanically, I prefer a system that has a fairly straightforward character creation system, without having to check multiple tables all the time. I like a building point system instead of random rolls, and a tier-based branching system of skills.

I.E., Intelligence > Linguisitics > Latin

Say the character encounters a loose page in a library, written in Latin.

A high Intelligence stat gives you a small chance to decipher Latin, perhaps at least the gist of the message. ”Danger ahead!”

A medium to high skill level in Linguistics gives you a moderate chance to decipher Latin, but perhaps not the subtleties. ”Warning: One of the doors ahead is dangerous!”

The Latin skill lets you automatically decipher the message, and depending on the skill level, perhaps notice a subtle clue.

Warning: The left door in the hallway ahead of you is trapped with poison dart in the keyhole.

Too many specific rules can overweigh a system. A solid general system, with flexibility for both player & GM creativity, is what I prefer.