You may not want to start with XIII, but again its all a matter of taste.

As some people have already said, I would go with IV for the DS (3DS)

Really hard to choose but I would choose FF9 in the PS Store. Its also somewhat 2 players if you have a partner that would like to join in on the command actions lol.

On PS3 (PSN): VII, VIII and IX
On DS: IV and VI

No order... play all.

4,6,7,9,10.

I've played 1,2,4,6 and 13.

I got halfway through 4 and 13 and then stopped.

I think I managed to beat 2, but 1 and 6 I only got to the final boss which were to powerfull and would take me a couple more days of grinding.

FF6 and FF9.

On the 360: Just play Lost Odyssey.
On the PS3: Just play Lost Odyssey on the 360.
On the 3DS: Just play Lost Odyssey on the 360.

Most people played VII first, so that's a good place to start, it's also the easiest one. Then I'd try IV, VI and IX. Stay away from VIII, X and XIII, hehe.

IX, X, Lost Odyssey. these ones and these ones only. youre welcome.

Play In this Order:
1) FF7
2) FF9
3) FF10
4) FF6
5) FF4
6) FF13
7) FF12
8) FF8
9) FF5
10) FF3
11) FF2
12) FF1

You must play every single one...no lie