One of the things that just drives me insane as a player is when you just know you're meeting one of the GM's beloved PCs as a NPC in the campaign.
You get a call from an unknown number, he hacks through your firewall and leaves a file on your comlink. You arrive at the location and there's the NPC. His bodyguards are decked out in milspec armor carrying assault cannons..downtown. Your decker tries to get some info on who the guy is, but his firewall is beyond milspec. Best of all, he's got the I'm-a-badass attitude #5.
I admit, as a GM its a whole different muscle to flex than as a player. You really don't get a lot of the RP in because your job is basically handling the world reacting to the players.
If you're more a player at heart and you have the world at your disposal its tempting to bring in a PC as a NPC and just impress upon the players how awesome they are. Its your world, Dreckkickula just happens to be a prime runner now with his own corporation behind him.
You should step back and pause a moment. While you might be having a good time RPing your old character the players are likely sitting there groaning thinking, "Okay, okay we get it. The guy is God. Can we get onto the parts where we get to be cool?"
A RPG is about give and take, its a social contract between players and GMs (I'll touch on this topic at another time). While setting a rich, vibrant world is part of that contract one the other parts is accepting this is the story where other people are the main characters.
If you really want to have a PC of yours be a NPC in the group, have them there as flavor. Maybe they're the gruff bartender that used to be a runner until he took a ... ahem ... turn at bartending. Maybe he's the pawnshop owner that just wants to trade things so he can feel like he's still in the game.
Don't make him, or her, a NPC that has dominion over the plot and the players. It doesn't often make them think the NPC is cool, it more often makes them resent the NPC because in their mind the NPC is that rich kid that is given all the new toys and rubs your nose in the fact you don't have them.