Wii Fit wasn't a console - it was a game on Wii, which needed the balance board. It can be played on Wii or Wii U (successor to the Wii) but not on Switch (Nintendo's latest console).
Microsoft's latest console is called, rather confusingly, the X-box One. The original was released in 2013.
They later released the X-box One S (a smaller and slightly more powerful version).
Recently they launched the X-box One X, which is even more powerful, and is the most powerful console currently available.
What's the difference between XBox and XBox live?
X-box refers to the console. X-box Live is the online service - you will need this to play games online. I think that costs 6 quid a month or about 45 quid a year, but I'm not sure. If you don't play online, you won't need it.
The PlayStation 4 equivalents are:
PS4 - base model
PS4 Slim - equivalent of X-box One S
PS4 Pro - equivalent of X-box One X, but not as powerful
The PlayStation equivalent of X-box Live, the online service, is called PS Plus. In the last couple of months, Nintendo have also started requiring a subscription for online play.
If you choose an X-box / PlayStation 4 and you have a 4K TV, I'd probably go for the Pro / X. If not, it depends whether you want to spend the extra money for a difference that isn't that noticeable on your TV.
No other accessories are needed, and the Switch comes with two "joycons" (controllers) so unlike the others, two people can play together out of the box. However, you might well want a carry case if you take it out of the house, a protective film for the screen and a Pro controller - the joycons are a bit small for adult hands, I find.
X-box is better for driving games (semi-serious ones, like Forza Motorsport and arcade racers, like Forza Horizon). It also plays many games from older X-box models. See this list.
www.xbox.com/en-US/xbox-one/backward-compatibility
PlayStation has more exclusive games than X-box, but there are more than enough games released on both to make that a non-issue for most people.
Nintendo's strength is in the Nintendo series games - in particular, Mario and Zelda, but there are other excellent games on the system. The other advantage is being able to play your Switch without needing a TV.
I'd suggest basing your choice on three factors:
- Is using your console as a portable important to you? If yes, get a Switch.
- Do you want to play online with your console-owning friends? If yes, get the same console as the majority of your friends. This doesn't apply if you want to play Fortnight.
- Research the exclusive games for each system, and choose which ones appeal to you most. Some examples:
Switch: Mario, Zelda, Smash Bros (coming soon), Arms, Mario Kart
X-box: Forza, Forza Horizon, Halo, Gears of War, Ryse, Zoo Tycoon
PlayStation 4: Spiderman, The Last Of Us, The Last Guardian, Yakuza