As far as big racing games from 2017 are concerned to if the biggest titles from that year that comes to mind are Mario Kart 8: Deluxe and Gran Turismo: Sport. While GT: Spirt was the highly anticipated sequel of Gran Turismo 6 which was released back in December 2013 Mario Kart 8: Deluxe was basically the Switch version of MK: 8 which came out on the Wii-U in 2014. As far as overall excitement is concerned many people would definitely give the edge to Mario Kart 8: Deluxe over Gran Turismo Sport especially since it has received way more mainstream both in 2017 and 2018. In fact, Gran Turismo: Sport was over shadowed by Forza Horizon 4 which came out back in October 2018.
As far as sales are concerned Gran Turismo Sport has managed to reach at least 3.3 million copies which is very impressive. However, Gran Turismo: Sport has yet to reach 5 million in sales the amount that its predecessor had surpassed following its release in 2013. Seeing how the Nintendo Switch was arguably a more popular game system than the PS4 was back in 2017 many would definitely argue in favor of Mario Kart 8: Deluxe on being the more popular game overall.