From what I have heard:
Grand Slam Tennis is a bitch early on, and it takes some time (a few hours) to get past an initial learning "block" before you start to appreciate it's controls/gameplay.
(I am imagining this "block" to be similar a the one I found with Wii Sports Boxing, in that you get to a point where you can't figure out what you are doing wrong, but for some reason things just don't seem to work very well.... but if you push through it like I did then it is very rewarding... unfortunately GST seems to have this block pretty much immediately, wheras Wii Boxings early opponents were so stupidly easy it didn't really matter that you hadn't figured out the controls yet, so GSTs downfall seems to be it really should have had a training mode of some kind)
Virtua Tennis is apparently more like Wii Sports Tennis but with more ball control, in that it is more about timing and fast play, rather than methodical ball placement.... It's downfall seems to be a poor online in comparison to GST though.
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Tiger Woods 10 however I have heard almost no bad things about it... and despite it originally being low on my list of wanted WM+ games due to it being golf instead of tennis, or Wii Sports Resort.... I think I am more psyched for it than even WSR now.
