2017.
2014 had some good games, and kicked off the generation but otherwise, is kinda forgettable.
2015 had The Witcher 3 and Bloodborne, which are great games, but other than that, that's all.
2016 had the odd great game, but other than that, nothing is to note about the year.
2017 is the best of the years. Games like Super Mario Odyssey and The Breath Of The Wild make it one of Nintendo's strongest years, other games like Resident Evil 7 and The Evil Within 2 make this one to remember.
2018 had Spider Man as it's best game, God Of War is also to note, along with other games, but it's not as good as 2017.
2019 is kinda boring. Death Stranding and Resident Evil 2 are the highlights of the year where the hype for the next generation starts.
2020, the end of the generation, has some great games, like Half-Life: Alyx, The Last of Us II, Ori And The Will Of The Wisps and Cyberpunk 2077, but 2017 just edges it out.
If I had to rank them, then it would be 2017 > 2020 > 2015 > 2018 > 2014 > 2019 > 2016.