This has been my favourite so far.

Nintendo fans - Nintendo is not milking their mascots

Microsoft fans - PSN is waaaaayyyyyyyyyyyy behind Xbox Live

Sony fans - every games that are not true exclusives/arcade/indy/console exclusives/kinect are not worth it

Nintendo fans: The belief that stories automatically make a game not a game.
Playstation fans: Their infactuation with graphics.
Xbox fans: Their belief that Kinect will get some core games.

nintendo fans: they think gamers play the wii

sony fans : they think games like uncharted and infamous hold a candle to gears and halo

xbox fans: think halo and gears is enough exclusives, also thinks GOLD membership is a better deal then PSN+

Sony Fans : Saying Uncharted 2 looks better than anything on PC. And other similar comments.

MS fans : XBL is better than PSN (and any other online service) because you pay for it.

Nintendo fans : All Nintendo first party games are above every other game on this planet.

MS fans: Xbox live money is used to make new games

Nintendo fans: Nintendo makes the best games. Period.

Sony fans: The vita isn't fucked

MS fans: we actually have games and Live is the best thing Evurrrr, for 60 dollaz/year

Nintendo fans: Wii is actually current gen, Nintendo invented videogames

Sony fans: Not having enough money to buy all exclusives

Nintendo- Claim that the only thing that matters with graphics is artistic design while disregarding the technical side of things.

Microsoft- Think that paying for online is great.

Sony- Always want bleeding edge tech no matter the cost. (myself included)

MS fans:

paying to play games  online is acceptable. (Especially considering most of the games don't even have dedicated servers)

microsoft making smart business desicions actually benefits us gamers. (I don't care that they are making a lot of profit with kinect, I want more good games)

Exclusive XboxLiveArcade games make up for the lack of exclusives. (They are nice and all, but very few stay exclusive for long)

Sony fans:

Reviewers that give xbox exclusives good ratings are being payed off(seems silly they didn't do that with kinect starwars considering how much it was marketed)

Reviewers that give ps3 exclusives any score below a 9 clearly don't have a clue, or hate sony.

TROLOL enjoy yet another gears of war or mario game loserzz. OMGZZZ I can't wait for the next uncharted and god of war.

Nintendo fans: 

Nintendo made a good decision by making the wii seriously underpowered. (Good business decision yes, but for actual gamers it was horrible. I feel sorry for any gamer who only owns a wii and missed out on many of the amazing third party titles)

Doesn't understand why hd gamers only seem to buy call of duty. Can't wait to buy the next 2d mario and pokemon game (Seriously nintendo, you don't release these games every year so why the hell are they all nearly identical to one another.I understand that sequels will be similar. But to be honest even activision changes more with their yearly call of duties than nintendo does with its mainline pokemon games.)