I hate to be a downer, but the odds of you ever becoming better than Steve Vai are extremely low. Even if you excel in your playing, he will always be a step ahead of you. Don't really take this as an insult, because there are very few guitarists out there who could measure up to Mr. Vai. Even those who are better than Vai, technically-speaking, still have a lot to learn when it comes to tasteful playing and creativity. Having said that, you can still become quite a good guitarist. Your best bet is to practice. Practice EVERYTHING with a metronome. Judging by the guitarists you mentioned as your inspirations, I'd learn all the scales across the fretboard (in every key), basic arpeggio patterns, advanced arpeggios/sweeping arps, string-skipping techniques, all 3 major picking styles (i.e. alternate, legatto, and economy), sliding patterns, bends, vibrato, harmonics, pinch harmonics, natural harmonics...hmmm...lol....did I miss anything? That should keep you busy for a long time. :)