You say you practice 3 hours a day but you didn't for how many years. That counts for a lot. If you are self taught then there is no telling how many bad habits you've developed. Time may not be the biggest issue. When we practice we reinforce patterns and if, as you say, you are always sloppy and not smooth and you keep practicing in the hopes that it will clean up then you are really reinforcing "sloppy" as a standard. If you had gone through a graded curriculum with an instructor, or self taught with high quality resources, you might be able to avoid this.
You mention playing guitar "faster". Speed comes from practicing SLOWLY. SLOW --> SPEED. You need to understand that in order to play something fast it needs to be so deeply programmed into the muscle memory that it is automatic, as easy as breathing. Until you have something memorized to that level attempting speed is useless. Take a scale run, or a lick from a song, that you are trying to master. Spend about a week playing it 100s of times a day so slow that you can't play it wrong, e.g. one note per second (that's right 1 per second). Play with your hands and body relaxed but not totally limp (you still need good posture and correct hand position). Get it to the point where you can hear it in your head when you're not playing, and can mimic the movements without the guitar. Then after you've put in several 1000 reps start playing it in time with a metronome. I should have asked or stated in the first place, use a metronome (are you?).
When it comes to pushing the speed of a piece that you have memorized there is a standard trick. Start at a speed where you can play it without any tension in your body (this is after the week or more spent on drilling it into your memory) and play it a few times at that speed. Then go up 2bpm and repeat, then down 1bpm and repeat. Continue on this path until you are 20bpm faster than you started provided that you don't start making mistakes or getting tense. If you do then stop at whatever speed that happened and make a note of it. Every day do this same exercise but starting at a higher speed. If you're luck and you got 20bpm faster without problems you can start the next day at that new speed and push it another 20bpm. This approach works very well for developing clean and accurate speed on any instrument. It probably works for dancers too, working in complicated sequences.
The above practice advice assumes that you at least have a solid foundation in the basics. That you have developed finger independence and have good hand posture, not squeezing too hard, not putting the thumb over the edge of the neck, etc. It also assume that you have put in some time in developing basic technique. If you have not developed these basic attributes then your approach may be self defeating. In learning an instrument like the guitar it is important to divide up your practice time into a few categories. These might be something like;
(1) Basic hand movement exercises. This is not even music but the athleticism of guitar. You can find 1000s of exercises that go back 200 years or so. The exercises in all modern books are the same as Tarrega published for classical guitar in the 1800s. Things like hammer on pull off chromatic exercises up the neck, the 1-2-3-4 exercise, "spider" exercises. You will find exercises for the picking hand too, alternate picking, string skipping, finger picking etc. Some of these are done on the open strings. The point of them is to teach your fingers to move correctly and your pick to locate the correct strings without the added burden of trying to play a song. The guitar is hard enough. It takes time and patience to get skill on it.
(2) Basic music exercises. These would be the basic rudiments of music (and probably the same for all instruments), such as the major scale, playing intervals in sequence and together, simple open string chord forms. Most graded method books, e.g. Carcassi, Mel Bay, Levitt, provide a set of common exercises in each key. Carcassi has the scale, the I-IV-V progression (or cadence), then a simple scale exercise and an arpeggio exercise, then 1 or 2 simple etudes that are hard enough to be a challenge for the beginner but not so hard that they kill you and not really worth making part of a repertoire.
(3) Simple and complex pieces. This would be comprised of musical compositions that could be part of a musician's repertoire permanently. Such pieces would require that the guitarist had at least developed some mastery of the first two categories. A performance piece might takes several months to learn and get clean.
(4) Techniques and technical exercises. This can be thought of as a more advanced version of the first and second categories. The intent of the first category is to get the hand moving they way you want it to and in many cases one doesn't even listen to the guitar. Classical guitar books will tell you to mute the strings. You're only "feeling" your way around the instrument. The technical exercises might involve complex musical patterns that are designed to give you exercise in a specific technique like, alternate picking, consecutive picking, sweeping, slurring, tapping. These will also work your endurance.
There could be more categories and different guitarists may agree or disagree with my division. In all of these cases it is important to use a metronome.
A lot of modern "self taught" guitarists never go through any of these training exercises and just go for category (3). Like a total beginner wants to learn Eruption and thinks if they just try hard the technique will appear one day. That usually does NOT happen. Even the greatest guitarists and musicians in the world will tell you that after 40 years of training they begin each practice session with category (1) basic movement exercises. These transform the body and everything is perishable so it needs to be reinforced forever. I would not worry if you think that your friends play better than you with less practice. They may have used their practice time more wisely, have more years experience, have more effects on their guitar, etc. It may be that you are just frustrated and comparing yourself to other will not make that better.
I would not recommend practicing less, but practicing more intelligently. Get a routine written on paper and follow it daily. Pick a set of basic movements as a warm up, a set of scale exercises for practicing music, and a few pieces you want to learn and get better at. Use the metronome and following 2 up 1 down method for speed. Make sure you isolate specific movements that give you problems. Perhaps the songs you play are cleaner than you think but one spot always comes out like crap. It could be a string skip or a sweep that you're are not good at. If so then get your hands on some basic movement exercises for that technique and drill them. Then your song should get cleaner too.
