Metal Gear Solid is a Sony franchise, despite what all of you are saying. We don't really even have to study Metal Gear 1 and 2, since they are not part of the Solid franchise, but let's look at them anyways. The games originally came out on the MSX2. Sony just so happened to have been a pretty large developer of MSX2 hardware. Look at the Wiki for MSX. Is that a Sony? So Metal Gear ran on Sony hardware before the NES ever got the game.
Moving onto Metal Gear Solid, it was a PS1 exclusive. A generation later, Silicon Knights headed development of Twin Snakes. Twin Snakes came out a generation later, so it's not like it's a big deal affecting the franchise as a Sony franchise. The remake has lots of issues too. The first-person aiming breaks the game in some instances (most famously in the Ocelot boss fight). Moreover, they sort of messed with Snake, giving him the power to suddenly dodge bullets for some reason. I really don't consider it a proper entry in the series. The cutscenes were made by Ryuhei Kitamura. He loved bullet time and utilized it far too much.
Alright so now we'll go onto Metal Gear Solid 2, a PS2 exclusive. Shortly after, Metal Gear Solid 2 Substance came out on the Xbox. A couple of months later, it came out on the PS2 with the skateboarding part added in as well.
Then of course MGS3 and MGS4 came out on Sony hardware. MGS3 Subsistence had MG1 and 2 on the disc as well.
If you've played the entire MGS franchise, it's been on Sony hardware. Sure, the franchise had a couple of bastard brothers on other consoles, but that still doesn't change in my mind that it's a Sony franchise.