When choosing a guitar, it also helps to know what kind of music you want to play. Heavy distortion is (arguably) best achieved with dual-coil, humbucking pickups. The Gibson Les Paul and Gibson SG lines are great examples of guitars that utilize humbuckers well (Ace Frehley of KISS, for example, has rarely been seen with anything but a Les Paul and Angus Young of AC/DC has used an SG for years).
On the other hand, single-coil pickups are typically viewed as best for clean, punchy tones. Think of Buddy Holly with his Fender Stratocaster or an endless number of funk musicians who also relied on Stratocasters. Also, there's a reason Fender Telecasters are common in country music -- the bright tones coming out of those single-coils are distinctive. Jangle pop musicians, blues artists and a whole lot of folks rely on single-coil guitars to achieve their signature sounds.
Of course, the single-coil vs. humbucker debate isn't so simple. Jimmy Hendrix, for example, is commonly cited as a guitarist who had a huge impact on the development of heavy metal and he relied on a single-coil Fender Stratocaster to achieve his distorted, fuzzed-out sound.
Picking a guitar is tough, huh? I prefer a Stratocaster with a humbucker in the bridge position, but that's just me.