You pretty much have 3 choices at this moment. A New Beginning, A Tale of Two Towns, and The Lost Valley.
Story of Seasons will be coming out at the end of this month (for NA, I know of) and that will probably be your best option.
Out of the 3 you could get right now, I've played A New Beginning and as an owner of 15 Harvest Moon titles, I was really disappointed by that game. It was really geared toward beginning Harvest Moon players, so I was disappointed but if you're trying to get back into the series, I think it's an excellent game.
A Tale of Two Towns looked kinda boring to me and when I read a lot of negative reviews about it, I decided not to try it out. And the same with The Lost Valley. It's kind of just a game they put together just to slap the Harvest Moon title on so hopefully players would see the title and assume it was going to be a great Harvest Moon game. But it looks pretty terrible to me.
If you want to look into the games some more yourself, I personally love using
http://www.fogu.com for tons of Harvest Moon information! These are just my opinions, and I haven't tried all the newer games, so I encourage you to try out the website.