Okay i've given Wii Sports a thorough play through
Tennis: Fantastic multiplayer experience, i'm pretty even when playing against my girlfriend (even though she doesnt understand the rules of tennis). The feeling that you're in the game is amazing.
Bowling: There's so much skill involved in this and i play Wii Bowling exactly the same way that i play the real thing, ie terribly. But i am improving!
Baseball: The timing of the swing is extreme, i am not enjoying this one as much as Tennis
Golf: A pretty simple golf game that i am secretly enjoying when in multiplayer
Boxing: Wow what a workout. I've had no arm problems playing any other Wii game (i also have Play, Zelda and Rayman) but after one game of Boxing it felt like my arms were going to fall off. Its the most frantic of the five games. If you have excellent reactions and timing you will have an advantage but my guess is most players will just flail their arms as fast as possible
The training and testing minigames complete the package.
If there was one thing i would have added it would be more single player options, for instance choosing which Mii's the CPU plays as in Tennis. But its a small complaint.