If you enjoyed Ghost Squad in the arcade then you'll like the it on the Wii, it's short but then, so is the original. They added some unlockable costumes to try and add a bit of replayability so if you are a completist you'll find a fair few hours of replay there.
HoTD is a great game, especially as you get 2 and 3, and it's actually quite hard (haven't completed it yet, always die just as I reach the end of game boss!).
I think to get the most out of both games, you need to be playing with a friend as it adds so much more fun as you can help each other out, brag about getting the best scores etc etc...
You also definitely need to do the IR calibration and then turn the aim cursor OFF (just as it would be in the arcade) - if you play with the cursor on then it ruins the experience completely.
If you like 'on rails' shooters then I'd recommend them both.