Good Simple Games For New GMs?

[Great Dragon]

For non-D&D and non-complex gaming, I liked:

Unisystem is a generic role-playing game system created by CJ Carella and produced by Eden Studios, Inc. It is used in CJ Carella's WitchCraft (I liked playing and GMing) - Armageddon: The End Times, All Flesh Must Be Eaten, the Buffyverse role-playing games, Conspiracy X, and several other games. Games designed using Unisystem have been nominated for, and won, Origins Awards.

The thing I liked was the Success Levels.

Actions are resolved by adding together the character's relevant Attribute, the applicable Skill, and a ten-sided die roll, plus any modifiers for difficulty; if the total is nine or greater, the action succeeds. Gamemasters (called "Chroniclers" in Classic, and "Directors" in Cinematic Unisystem) are also given tables of successes: characters that get a higher roll than the required nine have bonuses on their final outcome; this table describes how successful they turn out to be, and gives guidelines to figure out the resulting bonuses.

Sure, not every possible Action was listed, but at least gave an idea on how to figure out bonuses and outcomes.