Idk that I have a "favorite" so I will list my issues with all 3.

Nintendo - Not enough new IP's, releasing stopgap consoles 2 gens in a row.

Sony - Killing off amazing games like SOCOM and Twisted Metal thanks to milking them and rushing them. SOCOM especially, rushed out 4 PS2 games when it probably should have ended on PS2 with SOCOM II (my all time fav online game) and gave Zipper time to make SOCOM 3 for PS3. Instead they rush out SOCOM 3 and an expansion game Combined Assault and get some shitty developer I don't even remember to make the first PS3 SOCOM. Rushed out Twisted Metal on PS3 knowing the online play was broken.

MS - Killed off some amazing sports IP's and a couple more with good potential just to appease EA and get them on Live. Links was the best golf game ever, Rallisport the best rally game around at the time imho, and NFL Fever/NBA Inside Drive were getting good. Also failed with Crackdown.

Life for you as a gamer must suck then. That is, unless you really love old Atari or Colecovision games!

Or you're a bitter Sega fan?

They forgot what 360 was all about

Playstation

-PS3 was a huge risk that destroyed whatever money made by PS1 and PS2

-PSN took far too long to recover from the hacking in 2011

-Poor marketing of games, Vita etc.

Nintendo

-Tries ideas that are too radical and likely not to get decent 3rd party supports

-lacks key 3rd parties titles found on Xbox and Playstation

-Focuses far too much on Mario to bring success for it's hardware

Xbox

-Focus on non-gaming aspects of it's consoles

-Introduced idea of charging for online and made it acceptable

-lacks a good range of 1st party IP's (mostly FPS or Racers)

Um no, the title clearly says say one negative thing about your favorite console maker so I said something negative about the big 3 and PC. 

Killing every mascot.
Or not making great games great real mascots.

CRASH FUCKING BANDICOOT

Give me too many awesome games so that I struggle to make time for more important stuff in real life.

... Oh sorry, I thought we were following the OP's example.

If not, then this: incredible mis-management of the vast majority of their portfolio of franchises. Sure, they seem to make more new franchises than either of their competitors, but they seem to be killing them off at a faster rate too thanks to a legion of terrible decisions; or simply cancelling them outright for no good reason.

Nintendo tries way to hard to please mainstreamers and therefore their games get streamlined..... NSMB boring level design Mario Galaxy 2 no hub world. Metroid Prime 3 no connected world just levels to chose from SkywardSword no connected world just levels to chose from etc.....

Nintendo is so stubborn at times it can really hurt them