I'm a NintendoSoft gamer - so I can't speak for myself as a one platform holder only kinda guy.
I get Nintendo for the first party/Japanese stuff - MS for the third party/superior online/Western games.
I was a Sega and Nintendo "guy" until 1995 when I went Sony - until gen 6/2002 - (when I owned XB, GC and PS2) - and found myself won over by the diversity and quality of the combined XB/GC library over the quantity of the PS2 library which was rife with quality 3rd party exclusives but lacking in first party I cared about (God Of War arrived a year or two later, by which time I saw it as an inferior/simplified Ninja Gaiden. Even preferred DMC1) - and often those exclusives would eventually show up on one of my other consoles in a superior version (GTA 3/VC/SA for example), and I'd regret double dipping.
At the start of gen 7 - the 3rd party exclusives on Sony platforms that i cared about dwindled (though I guess I still like to play MGS4 among others) - and since most of the studios Sony pacman'd up in gen 6 (ND, Guerilla, SuckerP) hadn't really got started - there were no first party IPs I really cared about for the first few years of gen 7. Though a worthy PaRappa sequel ( Lammy2? They messed up Parappa2, which probably led to my disillusionment in Sony first party back in 02) would probably have tipped me.
All said - just one guys experiences and opinions from my 38 years.
Anyway - that's basically why I'm a MS/Nintendo guy - not really an answer to the OP - so in an attempt to answer that - I'll give my impression of what each single platform "fan" likes about his chosen platform.
Nintendo guys - Love the IP. Are rarely let down in first party quality hence their loyalty. And they like a sturdy system.
Sony guys - Love anime licenses/Sony first party. Larger share of under 35s than MS. More likely Apple fans.
MS guys - Larger share of over 35s. Probably gamed on DOS in the 80s. Value system /network stability. Less likely to be Apple fans.
My opinions. All anecdotal.
