Savage Worlds: As they've said, it's a winner if you want a quick pick-up system.The rules are easy to grasp (roll 4+, the die you use depends on your ability), everything is based on skills with "edges" serving both as feats and as classes, and the "advanced" rules are very modular, so you can add or remove anything you want.
Downside: it's not really "generic", because it's rather centered on action-heavy (not the same as combat-heavy) games.
Fudge: If you like tinkering, this is your game. As Savage Worlds, it's skill-based, and in fact you can use with Fudge anything meant for SW, just keeping this in mind: Mediocre=d4, Fair=d6; Good=d8; Great=d10; Superb=d12. It's more generic than SW in that you can really adapt it to any genre you want: Detailed, broad, combat-heavy, rp-heavy, gritty, four-colored...
Downside: If you don't like tinkering, this is
not your game, and you'd be better off picking SW.
Basic Role-Playing:
The skill-based rpg system. Very detailed, very solid (25+ years of history and it's
really still ze same

) and very light (roll d100 equal or lower than your skill).
Downside: Maybe better for "gritty" or "realist" games than for high-fantasy or superhero.
Risus: You can't get any lighter than this! It's more description-based than skill-based, but this makes up for even more freedom in character creation. Its openness is the highest I've ever seen in a rpg, so if you like freeform games this is the perfect choice for you.
Downside: Not very suitable for long-term games.
That said, I don't think there's "one" perfect rpg rulesystem, as each genre or playstyle has different needs, and what's good for one of them is bad for another.