[eberrong]

A lot of the big guitar tone typically comes from layering several tracks together. As a start, try recording the same part onto 2 separate tracks (in perfect unison of course). Then pan the parts somewhat L & R. Sounds "bigger" right? Some people layer 3, 4, 6, tracks together...whatever works.

Also typical high gain guitars are recorded from a 4x12 cabinet (usually closed back). I'm not saying that it can't be done other ways, I'm just saying that this is how a lot of people do it and get great sounding tracks.

Also mic placement is a big deal. Moves of 1/4" can have a big effect on tone. I point a SM57 directly at the cone (about 1" from the grill) and start to move it horizontally toward the speaker surround (edge of speaker). Somewhere in that sweep is a good balance of the bass and treble coming from the speaker. For me, it is usually closer to the cone...YMMV

Also as imacgreg pointed out. A lot of modern rock music is done with the guitar and bass working together as almost a single instrument. I find that huge sounding guitar tracks do not fit into a mix properly. I almost always high pass the gtr tracks at 100Hz or higher, which does not make for a huge sounding track (almost lo-fi sounding when soloed). But when you mix in the bass gtr and other instruments, it sounds great!

Last but not least, quality mic preamps are very important for recording distorted guitars! API, Phoenix, Great River, Chandler, any of these should do the trick. Anything less, good luck. IMHO, you will be fighting a losing battle.

Hope this helps!

PS - Also new tubes for the amp and new strings for the guitar can have a big effect on tone. They should be replaced before any serious recording sessions.