Why?
1. ZeldaBOTW - First foremost this is one of the best games ever created. Not to say there are some out there who won't think its their cup of tea, but its sales, ratings, and ability to sell consoles proves my point.
2. Good Selection - When you look at the quality of ports and new IP plus that it launched over the time when game launches are little to none, it has a superb launch library. All signs of success and the latest additions demonstrate that will only get better in 2018.
3. Solid functionality - The flexibility of the system design to be a home console or portable with no complications or pre-reqs is an amazing feat on its own. Then you consider the fact that it is 100% a game console. No other messy functionality. Plug-n-Play at its finest.
Those items are not mentioned to suggest it doesn't have room for improvement. I expect the game library in regards to AAA 3rd parties to narrow the gap a lot in 2018. Sure, pixel to pixel comparisons will obviously remain in the others camp. But the added feature of portability plus solid framerates/gameplay will be good enough to many and will continue to propel Switch in sales. As with any game console, games are all that really matter. You have the content at comparable gameplay and majority of consumers will go with what functionality is more important. In this scenario, I'm betting most will love the Switch primary difference (home + portable).