Personally, I've always found Microsoft fanboys to be the worst. They just seem the most aggressive. In my experience, I don't see a lot of Sony or Nintendo fanboys actively hoping for Microsoft's demise, yet I see Microsoft fanboys relishing when sony fails, or are otherwise HOPING for sony to fail at every turn from the original PS2/Xbox argument right to now, where I still see t hem actively trying to convince everyone that the Vita sucks and needs to die.
Before I actually knew how well Sony did with the PS2 (best selling system ever), I actually thought the Xbox was outselling it because many of my friends were strict Microsoft fanboys that hated sony, and were always spouting some nonsense about how the PS2 was a failure and all the good games were microsoft exclusives. Meanwhile, that system barely outsold the Gamecube, a norotiously poor selling console.
Then this generation came out and Microsoft seemed to have a thing with sony again, and for YEARS the Microsoft fanboys (and admittedly many of the sony ones) were screaming "PS3 HAS NO GAEMS", bemoaning the company for EVERY decision they made (they still do this) and basically doing everything they could do demonize sony and their prodcucts.
Microsoft fanboys are the reason I entered this generation HATING the Xbox 360 (them and the red ring of death), even though deep down inside I wanted one. Eventually I grew up (right around the time Sony started selling more consoles and Microsoft started floundering, therefore giving the Xbots no ammo to work with), and I picked up an Xbox 360, and now I have all systems and I certainly think they all have their merits, even though my favorite is still the PS3. Most games, best games, Blu Ray, love free online play and PSP/PSV cross connectivity. Going into next gen, I currently have the WiiU as my least favorite, but like this gen, I will get one, just not at launch.
Another annoying group of fanboys in second place have to be the "PC God Elitists". not people who simply think PC gaming is objectively better (for those with good systems it is better), but those who feel they have the right to look down their nose at console gamers, like they're above console gaming, BETTER than us. PC gaming is cool, and Steam has come a long way towards making i t far more user friendly, but I still prefer consoles to PC, and there's nothing worse than an elitist.
Apple fanboys are annoying, too...but I can ignore them becuase I know they're just a silly cult following overpriced nonsense that perfectly encapsulates all that's wrong with modern consumer culture. They're easy to disregard.
I got it all, baby!
PS4, Switch, WiiU, XBO, PC
Vita, 3DS, Android
Top 3 this generation:
Bloodborne, The Legend of Zelda: Breath of the Wild, Dark Souls III