Stuck in a rut. Don't know what to do to get out.

Well we ALL get into a rut now and again, sometimes they dont last long other times they can last for weeks. For your situation I think learning another instrument would help you. I never played anything untill I received a guitar as a gift a few years ago. I still love the guitar but I started playing a little synth organ we had lying around and even though it is a horrible little thing it has help me with both composition and even playing the guitar. It makes you think in notes and intervals instead of frets and strings.

Secondly, play/write/talk with the people who are beyond your skill level. When I first got the guitar I was terrible trying to learn by myself. I started playing with a friend who at that time had been taking lessons for 5 years solid and playing for about 7. I got soo much better the first time I played with him and it has continued. Similarily, try to convince some of the not so serious people to play with you. You learn alot from teaching other people, and they sometimes give you a new way to look at things.

See, my strive isn't necessarily to be a great guitarist, or to even play guitar. I want to make music, of any kind and genre. That is what I love doing, and often times I find myself composing using Guitar Pro 4 more than I actually play.

You should practice towards a perticular goal, like me for example: I want to be an all around player in terms of technique, songwriting, etc. So I might practice soloing one day, another day practice classical guitar, etc. It seems like your main priority should be songwriting if that's what you want to do, that doesn't mean you can't study technique but i just think you should focus on songwriting. I recommend getting lots of matieral on songwriting, whether it be books or talking to other songwriters. As well, I would get into the habit of learning alot of songs because that has always helped me with songwriting (it gives you an idea of what can or can't be done in a song, in terms of structure, theory, etc.)

...See, my strive isn't necessarily to be a great guitarist, or to even play guitar. I want to make music, of any kind and genre. That is what I love doing, and often times I find myself composing using Guitar Pro 4 more than I actually play.

I haven't read many posts or threads where a person says they're more into making music than being a guitarist. That's pretty rare indeed - or at least it's not spoken of much and nearly always takes a backseat to technique or gear or whatever.

Kudos!!
It just seems that whenever I play guitar, I can create a base to something that would sound good, but in my mind I can't incorporate other instruments into the frey. That often times leads me to overcomplicating what I am playing, and then usually it falls apart. However, when I use Guitar Pro to fill in the blanks, there's too many incongruities between actually playing, and what Guitar Pro gives me.

You're saying you can't 'hear' the other instruments mentally? Sometimes it doesn't just present itself. You sometimes have to pick up a bass guitar and start playing along to your main vocal/guitar track, and actually hear the lowness of the bass notes to get your inner ear going. Just one note sometimes and your mind clicks and goes "Oh yah, down here...

Same if you want to think high parts. You have to give yourself limits sometimes, like "only playing high, or only low." You can do your basic track and then capo your guitar way up high and force yourself to come up with high parts that might be translated to synth strings or something.

Or switch tunings and see what you come up with. It seems you're a composer/arranger at heart where you want to hear all the pieces and parts working together, but the thing is, if you went to music college and took up arranging, you'd find yourself taking a bunch of classes that weren't on your main instrument. Things like brass tachnique, beginning strings, percussion - all so that you, as the composer, will have a better idea of what each instrument is capable of, where it's 'sweet spot' is, its best, strongest range, and know how to write for it when the time comes. In lieu of that, you can get a lot of stuff learned and done by overdubbing, by getting into at least bass guitar, and for sure - a keyboard/synth/piano. Probably if you had to make a choice between bass and keys, you might want the keys because the modern ones, even the inexpensive ones (but with full-sized keys) can give you lots of textures to play around with.

The answer to how do I start making music has become kind of apparent, and I believe that it involves playing with other people. The only problem with that, is that I don't know that many people that play an instrument, and if they do, they're either not as serious about making music as I am, or so far beyond my skill-level that asking them to play something I've written would be boring for them.

Yyyyaaahh, in a way. It's a good thing to play with other people but if the opp doesn't present itself, and the only other option is to NOT play or write anything, just (as much as possible) BECOME the other person. Like do a few tracks just on guitar and singing, then get a bass guitar (or keys), and not touch the guitar for a few days and just come up with other parts. Lay them down, listen to them, redo them, relisten. It's really fascinating. After awhile you start to get used to taking the other player's role in the 'band', and start to think like a key player or a bassist and things start to happen.
Basically, it just seems to me that no matter how skillfull I become, how many playing techniques I play and get quite good at, my music-making is still in a rut, and that's what I want to improve.

Does anyone know how to do this that doesn't involve other people?

Be your own band. If there's no alternative as stated above, then just go for it. I do it all the time and I actually like it better than working with other musicians. In all my years of playing I've only worked with maybe 3 (tops), that I could just let go and feel confident that they'd come up with good parts. I haven't worked with a lot of musicians, maybe 50 all told, but just those 3 would come up with stuff that would make me think "Okay, I wouldn't've been able to think of that one; that's good man."

And with all the multitrack stuff nowadays, and all the relatively inexpensive instruments on the market, it's way easier to make your own kind of music. Nothing like playing back a guitar track on a mono cassette recorder and then playing along with that into the mic of a 2nd mono cassette recorder. :)