Like the real world, you'll probably find friendships that are eternal, ones that are on-again-off-again, perhaps with a love/hate oscillation, people who are shallow (or consider you shallow, after a while) with whom you can have bright friendships that burn out quickly, etc, etc...
The different is scope. The Internet is massive. You have a few billion people you might want to be friends with (possibly your soul-mate is out there somewhere, etc, etc) but the chances of any particular potential friendship being realised is small, and if there's a falling out its easy (assuming that neither party deliberately stalks the other for the duration, or you are actually both interested in exactly the same things and aren't willing to move away from your shared haunts) to lose contact entirely, just by not being in the same place as you were before (or, if you were, being there under another name).
There are some people I really knew that I lost contact with not through choice (mine or theirs) in various online communities from a decade ago that I occasionally have looked in on and they're still there, but I think it would be creepy for me to arrive back again. But that's my insecurity speaking.
Anyway, compared with the people you go to school with (assuming we're talking about that kind of age), love 'em or hate 'em, whatever happens you know they're there if he stops being a jerk, or she stops cold shouldering you or they admit that you were right after all, and oh, you're so cool now, and they want to keep in with you again (yada yada yada). Also, ExFriend can't easily go missing from a shared class at the same time as NewGuy joins the class, looking so similar, and having the same sort of things to say...
But on a moment-to-moment time-scale, there's not much difference between RL and Internet friends, and you'll have the same spats. It's just probably that the Global Village has got so many people wandering in and out of it than your average actual village (or town, or even city, although the human mind can't deal with units much larger than a neighbourhood, anyway, even if some of those contacts are from a longer distance away). Friendships that survive this tumult can thrive (I have known a number of on-line->personal->physical->children relationship transitions...).
So what am I saying? Well, in many ways Internet Friends can be the same as Real Life Friends. But more dynamically so, and bonds that aren't as solid can break perhaps a little easier (without one or other of the pair having to physically move towns, for extreme circumstances), and perhaps you need to remember that. But, on the other hand, you may well get to meet more people who potentially mesh with you than IRL, and so perhaps you'll get some better 'meshers' than without this wondrous thing that is The Internet.
Have I solved your problem? Have I answered your questions? I don't actually think so, but all the above is true. (FCVO 'True'. YMMV, HTH, HAND.)
(Oh yeah, as to the game: if it's not the same game without the people to play it with, then the game probably isn't worth it. But who knows which new players are just around the corner. The emotions about 'being cut off' may be affecting you, but I've heard the same sort of thing about not being able to go to the same coffee bar or borrow books from the same library for much the same reasons, and that's without complications actually seeing the old friend pointedly ignore you and go to a different table/set of shelves. On the whole these things tend to resolve themselves, whether matters of the heart, mind, ego or whatever. "Time is a great healer", and all that, even if it's just scarring over a wound rather than actually re-uniting lost limbs. Perhaps not always, but I think there's a good chance. Stick at it and get yourself into a new 'gang', (or go and find yourself a new set of friends...) Look, I'm rambling again, and of course still YMMV, etc...)
Edit: Erm, yeah, what GlyphGryph just ninjaed, in far less words.