Nintendo Switch. Hard to say without too much to go on, but I'll give it a shot.
1. The Legend of Zelda: Breath of the Wild - Easy, given its status as the most prominent launch title by heads and shoulders over the others. This will depend on how the Switch sells I suppose, but I could see its reputation becoming similar to that of Twilight Princess which seems to be seen as a Wii game before a GameCube one.
2. Super Mario Odyssey - 3D Mario in all of its forms is one of the biggest drivers for Nintendo's hardware business, and Odyssey looks to be taking the series in wildly new directions while tracing its steps back to Mario 64.
3. 1, 2, Switch! - Nintendo's attempt to do what worked for Wii Sports and what didn't work for NintendoLand, launch with a smaller, quirkier game to sell people on the concept of the system itself. Whether it will be successful remains to be seen - my impression is most gamers don't care to have anything to do with it, but I could easily be wrong.
4. Splatoon 2 - Nintendo surprised us a little by announcing the next Splatoon title as a full-blown sequel rather than an updated port, but realistically it probably falls somewhere inbetween. If anything it says more of Splatoon's breakout success, surprising many and responsible for much urine drinking around here. Nintendo's message is perfectly clear, not only is Splatoon here to stay but we'll try our damndest to get it out as close to launch as possible. Xenoblade 2 or Fire Emblem Warriors could serve as other examples of this, but I think it's important to touch on another thing.
5. Mario Kart 8 Deluxe - Many gamers have made it known their concerns that much of Switch's early lineup would consist solely of old Wii U games repackaged for a new audience that likely skipped the fledgling console. While Nintendo's announced several original games, something like Mario Kart 8 Deluxe might prove the skeptics' point. Outside of a far more robust Battle Mode, MK8DX doesn't offer much new over the Wii U version, which in fairness was a pretty fantastic game to begin with. Still, for Nintendo loyalists craving something new, it's understandably deflating.
Obviously given that the system isn't out yet, it's a reasonable assumption that in a few years' time it'll come to be defined by completely different games. Once again, hard to say.