i got way more than one, but off the top of my head King of Fighters and Gundam Vs series...that one isnt even released in the US

Which one? victoty? MK2? Rebirth 1? or 2?

uufff, ok listen to me i dont want to discourage you but... if it still has the shrink wrap on... you may be better off reselling it at a store or to anyone else, you see HDN 1 is the worst PS3 game i have ever played, in fact before playing it i already knew it was bad but i didnt knew it was THAT BAD.

now i know this doesnt sound good, but you have to belive me when i say that the other games are FAR BETTER, (thats why i said that the leap in quality from 1 to 2 is the biggest leap ive seen in my gaming life), the thing is.. i dont want you to play the first game and get the impression that this is a SHIT series (because thats what you are gonna think after you play that game...), you are far better off getting MK2 or even better Victory.

also really important: the first game really isnt cannon so you wont miss on anything from not playing it.

yes, the game is really bad and it does not represent the current quality of the neptunia series, if you can sell it at a store or trade it for another game then do it, i really like the Neptunia series but you should start with any of the other games.

hmm not sure if everyone considers these niche but...

Roller Coaster Tycoon
Europa Universalis

This!

You are safer getting Re;birth 1 which is available on the Vita and Steam. Do not play the original PS3 version. Its not worth your time.

I suspect Re;birth 2 & 3 with the former being out already and the later announced for the Vita to get a Steam version down the line too. 

Does ZoE count?

Just saw this: triple hi-five?

Yakuza (easily one of if not the most underrated game series out there)
Tales Of
Harvest Moon