My unpopular vote is for Wii because while most games were utter garbage, there was many amazing games like Mario Galaxy, both Legend of Zelda games, and Super Smash Bros. Brawl. The Wii really made motion controls mainstream and after that, the Xbox and Playstation tries to replicate it. While Wii Sports isn't an amazing game, it utilized the motion controls surprisingly well and made for a fun experience. I know that my pick is pretty unpopular, but I'm sticking with it.

around $300 - $400, depends how good the system and games are

Bioshock Infinite

Absolutely, Watch Dogs 2, but AC Syndicate, Breath of the Wild, Skyrim, COD Modern Warfare, Legend of Zelda Oot, Team Fortress 2, Cities Skylines, and Mario Galaxy are amazing games as well, and I would have a hard time ranking my favorites.