Despite the hate on "Final Fantasy XIII", I bought an used and cheap xbox360 just to play it (but it's on ps3 as well), so I recommend it. You may like it for at least two reasons:
1) it's linear, so if you're not used to RPGs and huge maps to explore it may be a good starting point, because you won't get lost (and later in the game you WILL find a huge map to explore, with lots of optional hunting quests, but there's always a minimap)
2) it's a mix of turn-based and real time battle, meaning you wait your turn to act but also you will have to be fast to change the job/class most useful for that moment in battle, especially during giant bosses fights; if you're used to hack and slash, it may be nice to find similar elements in the gameplay
It's different from the earlier "Final Fantasy" titles, especially because those are turn-based (exception on FF12, I didn't like it so I won't explain it), but if you're not into rpg you won't have prejudice :) In any case, you can watch gameplay videos on Youtube, and it's standalone, I played it but never touched the sequels because I was not interested, but totally satisfied with the ending.
Good luck with whataver rpg will be your first, it's an awesome genre and you can find very beutiful stories, be it action rpg or turn-based or with mixed gameplay.