Stardew Valley is supposed to be excellent and out for PC.

http://techraptor.net/content/stardew-valley-review

Stardew Valley is one of the best games here period.

I have heard that Story of Seasons is a better game in general but I cannot confirm personally. Rune Factory games are always a safe bet if you ask me. Rune Factory 4 is, once more, supposed to be basically 3 but bigger and better with a couple of odd things thrown in (something like certain important events for the story are attached to random events).

Story of Seasons and Harvest Moon are the same franchise (sort of). The thing is, Story of Seasons is the original name of the Harvest Moon series in Japan, while Harvest Moon is the name Natsume choose to use when they bought the rights to publish the series outside of Japan in 1996, an agreement which lasted until 2013.

So what happened since 2013 - which might be confusing for a lot of people - is that Marvelous, the owner of the IP and developer of the games, decided to publish the games themselves, but under the original Story of Seasons name since they don't own the Harvest Moon name, while Natsume decided to start making farm sim style games and release them under the Harvest Moon brand.

So the latest Harvest Moon games Lost Valley, Seeds of Memories and the iOS spin-off Frantic Farming actually have nothing to do with the old Harvest Moon/Story of Seasons games and are sequels in name only, while the original series lives on as Story of Seasons.

Rune Factory is a Story of Seasons spin-off where they bring some action RPG elements into the mix, kind of like Stardew Valley.