I'll throw in my hat with the people who can't stand Shadowrun.
The thing is, the setting is
awesome. I'd have to think long and hard to find words to describe how much I love it. The mechanics on the other hand... The balance is awful, to start with. Cyborg "street samurai" are 1000000 times better than any other character type. Hermetic mages are ok artillery, but it's a game where it's far too easy to be killed by a lucky shot from a bad guy to want to play one. Adepts... Don't even get me started on their uselessness.
Going into the net is ok if your GM can handle two threads of story at once... But that's extremely taxing and the vast majority of GMs aren't going to want to do it.
It's not a factor in PbP play though
As for GURPS, I actually like it, sort of. I don't like their magic system (Spells cost fatigue points... you can cast like... 5 decent spells before you pass out. Not fun), and some other things, but I do like the point buy + advantages & disadvantages system. It does get bogged down though, and often times things aren't really balanced well. The superhero setting is great, but they want you to use the core set psionics rules, which just seem really weak in that setting. Things like that.
Someone mentioned Exalted earlier, and I have to say that I love it. It's actually my favorite system (Though it's hard/impossible to find a group). I love the way skill flows directly into combat damage, not just whether you hit or not. I love the way combat itself becomes a roleplaying opportunity. I love the whole kung-fu movie feel that having such a vast gulf in ability between "mooks" and actual opponents creates. I love the detailed martial arts styles, the way that everything is magical, the way that melee characters aren't just swinging, they're using their abilities almost every single round, and choosing between multiple options available. The extra dice for roleplaying an action well. Everything about the system clicks with me.
It's just too bad it's so hard to find a game!