How do I love thee? Let me count the ways:
1) Perfect price point. $10 to buy into the game, which is flexible enough to run multiple genres almost out of the box (and certainly with the supplemental material).
2) Fantastic setting support, including my favorite RPG setting (Deadlands, if you missed that post).
3) I love the power curve, which allows characters to become strong and capable, but without destroying verisimilitude in the world as they become devastating world destroyers like they do in other games (why do level 20/30 characters in some D&D games listen to ANYBODY again?).
4) I know how to "bend" the system to accomplish what I want, 95% of the time. The only other system I've felt anywhere near as comfortable in that regard is the Cinematic Unisystem.
5) I have personally ran fantasy, horror, westerns and supers with it, and each game managed to feel familiar, yet mechanically distinct.
6) I love building characters for it. That's part of the reason I did the Savage Worlds Characters Are All The Same series, and why I have repeatedly done "Half-Dozen Heroes" posts various settings.
7) The proof is in the fun. We have a blast with the game, and I have rarely had a bad session.
It is perfect? No. Can it do everything? Maybe, but sometimes you are bending it to the point of breaking if you do, and there's other games that can handle it better. But if you told me I could only run one game forever, then I would grab Savage Worlds and be set.