It would have also been more ideal if they'd released multiple colour schemed Vita's, over here on my island they only had the black model, back when we had the first ever PSP we at least had a choice of black, white and grey and the one time FFVII PSP.

Right, I think it was only in black when it came out, or white too..? I don't remember. Funny you mention the colors since they did release more colors later, and it's weirder that I don't really see people with any color but black. I kind of forgot the other colors existed...

It tried to be a handheld for Call of Duty gamers, which they didn't want. I mean, they refused to help Capcom with Monster Hunter, so there went their only system seller.

I think that's another issue more with marketing, since they didn't release the multi colour versions within the two stores on my island there was a lack of tv advertisement which could have pointed to online stores (which were able to be ordered) which would have benefitted a portion of possible customers, it would have done so for me at the time of the original PSP and would have for the Vita.

No really big exclusives, no Western support, proprietary memory sticks, 3rd party support, no real help from advertising and development from Sony, etc.

Pretty much the first 4 options in the poll.

I'm mainly referring to the user experience as opposed to the hardware. 

3RD party awful support

It lacked Tetris/pokemon/monster hunter type game that really moved systems on its own. I love it, but unless you love Japanese games like me then it is a hard sell for many people.

It was a conglomeration of things mostly around launch for me
1. They launched later than 3ds. When you're taking on a giant you can't be late to the party and let them establish themselves. MS coming early to 7th gen helped them establish a fanbase before the competition got there. With 3DS' initial struggles this could have really helped Vita be more even out the gate.
2. Letting MH go! This was huge for Japan and I think launching earlier would have helped as the 3DS wouldn't have such a huge marketshare to where they just didn't care to release MH on it.
3. Launching at $250. At least if you're going to launch later don't make the same mistakes! The 3DS couldn't sell at $250 there was no way Vita could. Also that 3g model. It was the same price as PS3 which I realize is supposed to be different but when they play mostly the same games people really lost incentive due to that price.
4. Lock down a IP around launch. GTA sold well on PSP. GT sold well on PSP. Either of those within the first year would have helped a lot especially in the West. They tried Uncharted which had no handheld userbase and after playing it I understand why. Get something that works on the small screen but still feels high budget. Normally that's an RPG of some sort or one of the two I mentioned. Lumines, SSD, and such are great but they still don't feel AAA enough to sell this dedicated machine to carry along with your smartphone.