FF XIII has zero gameplay in the first 12 hours. You run forward and press x. That's all. It's an absolute joke in my book, and if it had a different name it wouldn't have sold anything. The only redeeming quality was the (amazing) graphics.

The best advice I can give you is play Tales Of. Both Vesperia and Xillia far surpass the XIII series, and isn't a remake. Or wait till X.

I started with FF:Crisis Core on PSP - pretty darn awesome
went on playing FF:XIII - Realy liked it
Then started FF:XIX (since I never finished it when I was younger) and loved every minute of it
Played FF:VII - loved it
started FF:XIII2 - got bored after 12h
started FF:VIII - played like 20h and got distracted from other games but plan on finishing it
and then I will start with FF:X
everything I can play on VITA I play on Vita, as I can simply go into standby mode and continue from where I left off.

go ahead and just start the one that looks the best to you!

I'm not sure this is at all relevant anymore because this was quite a bump, but if we're really going to recommend games not listed, I'd advise him to get VI instead. I'd say that in addition to VII, VI is most often mentioned as being people's favorite in the series, and there's good reasons for that. And personally I think VI's graphics have aged better than VII's, so... In many cases, good 2D art simply ages better than 3D art.

If you don't mind old school graphics, then I would honestly start with VI or VII on PSN. If you want something newer, then either the X compilation, or if you don't mind MMO's XIV. Avoid the XIII series. While not technically bad games, they do a poor job of representing the series' quality.

Final Fantasy X HD is the way to go. I wouldn't personally bother with X-2 yet, as it was a pretty weird step for the series, so just stick with X, it's easily one of the best in the series, if not one of the best games ever made. Then after that, try and play Final Fantasy IX, it's also one of the best games out there, and it's easier to get into than VII because it still looks stunning due to its art direction.

Avoid XIII, XIII-2 and Lightning Returns like the plague. The drop in quality was ridiculous; everything that made the Final Fantasy series so strong and iconic was removed, and replaced with nothing of value. Shallow, boring, mediocre games, the lot of them.

So:

FFX
FFIX
FFVII

Get FFX HD and ignore the rest. It will be a waste of time. Get FF7 and FF9 on the PSN shop and play those.

Or you could just skip them all and get Ni No Kuni. You like Pokemon obviously, and it's a game made by Studio Ghibli. You CANNOT go wrong.

FFX's ctb system plays somewhat like pokemon, so it may feel more accessible than other ff games to start with.

FF13 and sequels are trash. I would give FF13-2 to you if I could. I may have thrown them in the trash though.That's how bad they were. FF died after 10. Play 4-10. 12 was descent, but not memorable.