Not just aisle, but it should be center aisle. In my experience, on most jet in a 2-3-2 configuration, the side aisle seats will have a support on both sides of the seat in front of you. OTOH, the center aisle will only have a support on one side (toward the center), giving you more leg room overall. You would think it would be the same on both sides of the aisle, but it’s not.
My handy diagram, - is a seat, _ is an aisle, and | is a support:
(–|--|–|--|–|–|--)
Window seat- the vast majority of the time, I’m curteous and lean back in my chair so the people beside me can look out the window too, but when I’m lucky and there’s no one next to me, I totally hog the window and can stare out there for hours. Even if we’re just over Iowa and all I can see are clouds.
What can I say? I’ve been on lots of car trips, and I did the same thing during those too. 
Window. Every time.
Reasons:
And I always grab an extra pillow and blanket or two if they’re available.
Maybe it’s because Australia’s such a long way from anywhere and all flights are long, no matter where you go.
When I’m not sleeping, I get up and walk a couple of laps of the plane every hour or two, and use the loo then - I’ll spend around 20 minutes out of my seat.
It sounds awful, but I figure I’ll never see the people I’m travelling with again, so I don’t care if they hate me (of course, this is not an excuse to be rude or obnoxious, and I always apologise, but I just don’t worry about doing what I need to do to be comfortable.
Window.
Because I’m small, slightly clasutrophobic (yes, you’re still stuck inside a metal tube but the window gives you the illusion of more space), and I never, ever, ever get tired of looking outside (except during pitch black night, which is why I bring a book for those trips).
I’m assuming we’re talking commerical airliners here, of course.
I’ve very tall, so I prefer the window as I can wedge myself into it during the boring bits, and look out of it during the interesting bits. I’m wide across the shoulders too, so drinks trolleys are my natural enemy. Actually no, food trolleys are. The drinks ones I can forgive. 
Isn’t that what the middle guy is for?
If you can’t fly first class, of course the bulk head seats are the nicest coach seats available, but those are usually reserved for the frequent flyers and you have to be in good physical condition, blah, blah, blah.
If you can’t get the bulkhead seats, ask for the row directly BEHIND the wing seats; you’ll get ~4 extra inches of leg room PLUS the person in front of you won’t be able to recline for safety reasons. (Tips courtesy of my friend, the Delta pilot.)
I prefer aisle mainly because I feel trapped when sitting anywhere else.
I used to fly window class because I enjoyed the view, had the wall, and seldom was bothered. (On LAX-SYD runs I will still take window class.)
Nowadays the aisle seat. The legroom is too cramped these days and an aisle seat gives me the room I need. In addition, since 9/11, I’ve experienced a few flights where we’ve had some wackos aboard and everybody gets into panic mode. It’s easier assisting the flight attendants when you don’t have clamour over sweaty and vibrating with fear passengers.
(Hell, if I’m ever aboard a flight when something really bad starts going down, I plan on doing a “Remember the Alamo” thingie. At that point there is nothing to lose.)
Aisle. I’m tall, so I like being able to stretch my legs into the aisle if necessary, and it’s nice to be able to get up and move about whenever I want without having to disturb anyone else.
I prefer the window seat. I like to look out and see what’s below. I also like to guess about where we are at and see if I can identify large landmarks, such as lakes, rivers, etc. At night I like to look at all the lights of the towns below, and I like to see the lights of the city I am flying into or out of.
Depends on the length of the flight. I’ve got a bladder the size of a pea so if the flight is anything over say, 2 hours, I’ve got to be on the isle. I can’t stand climbing over people in those iddy biddy rows.
Anything under 2 hours though, I’m a window gal. I like to see where I’m going.
Nobody has mentioned escape after a hard landing (crash). Aisle seat passengers tend to survive more often than window seat passengers. That said, I like the window, unless it’s a red-eye flight. Land forms really impress me, but I like looking out of the window even over the ocean. Leg room is not so much of a problem, as I have shrunk to 5’ 4" in my geezerhood. As to the other thing, I’ve lived almost long enough. 
I’m the opposite, though my long hops are normally 13-hour flights across the Pacific. On those, there’s nothing to see through the window except for a short time at the start and at the end, and most passengers try to get some sleep. I don’t feel comfortable waking two people up to go to the toilet, or just to walk up and down to get some exercise.
Window, because I feel less trapped. Also, I like to personally keep watch and make sure there is no deformed teddy bear tearing up the wing of the plane.
Both, when I can get it. For short hops from a small airport to a large one or vice versa, sometimes you’ll get a plane with 1 seat on the port side and 2 on the starboard. Sit on the port side and you’ve got the best of both worlds. Otherwise, I like the window seat- I like to look for landmarks so I can figure out where I am.
Aisle. Once you’ve seen one cornfield, you’ve seen them all. Meanwhile, if you need to get up or just want to grope people’s legs as they walk by, the aisle seat is better.
Window, because then I can lean against the window/wall and take a nap without having to worry about whether I’m falling into someone. Also less likely to be disturbed by someone passing in the aisle.
The need to pee does occasionally cause problems with this, although I normally skip my meds when flying over three hours, the antiandrogens because they make me need to pee and the estrogens because they increase the risk of deep vein thrombosis, which can be potentially fatal.
My experience is that leg room is the same in both aisle and window seats. It’s not like you can stick your legs into the aisle anyway. (Caveat: I mostly fly American, which offers more leg room than most airlines. Your airline may vary.)
Window seat. I’m a scenery junkie and can spend an entire multi-hour flight just staring out the window. I also like the fact that I can wedge myself into the corner and make my own little room.
Window any time. I like having something to lean up against. I don’t tend to need to get up for the bathroom except on the longest flights, so that’s not a problem. And I’d rather be the climber than the climb-ee… I once got stuck in an aisle seat next to two 10-year-old girls, who were up and down every 20 minutes during the entire transcontinental flight :mad: Evidently their parents had 2 seats in each of two different rows and thought the girls would enjoy sitting together and the hell with the people around the girls.
I may be in the minority but I really don’t like bulkhead seats. You may not have someone leaning back into your lap, but you really can’t stretch your feet out as much - not to mention there’s no under-seat storage.
If I’m flying with friends or family, I take the window. I like having something to look at when I get bored, and they don’t mind me climbing over them to use the restroom. If I’m flying alone and sitting with strangers, though, I prefer the aisle. I’m quite claustrophobic, so when it’s people I don’t know penetrating my personal space bubble, the aisle seat makes me feel like I have just a littttle more space.