Gosh dang, this game is fucking awesome.
I missed out on HOTD2 for the DC because I never had a gun, I missed out on HOTD3 because I never had an Xbox, so its all new to me and its all so frigging good. Even if I had played them outside of an arcade before, I'd still be loving it for the Wii because the control is just so fucking good. I'm popping zombie heads like nobodies business here, and it never fails to be completely satisfying when one of those skulls goes flying. Also, its quite amazing how well HOTD2 holds up, 10 years later and its not hideous to look at, how many 3D games can you say that about?
HOTD3 is just not as good, but not without its charms. I do like the very colorful graphics, nice to see something other then brown and gray. Also, it has a shotgun as the default weapon, which is awesome. There's some extra modes and such that keeps things interesting when the ultra-high and moderate challenge of HOTD 2&3 become repetitive. Its the most feature-packed, best light gun shooter I've played since Time Crisis 3 on the PS2. And this my opinion even after loving the shit out of Ghost Squad.
So to sum things up, HOTD 2&3 is the effing shit, and reviewers who lowballed it are lame and probably like lame stuff like drinking lame-en-ade.