bungie has done it again
It provides a challenge without being mind-numbingly hard, and is infinitely more strategic than something like Starcraft, where the easiest way to get things accomplished is to amass a huge force and just send them all in at once. If you try that in Myth, it may work, but that next battle in the level will be even harder seeing as you stupidly sacrificed some of your soldiers on a frontal assault.
The graphics were good, even with all the units rendered as 2D sprites. The sound fit well, from the narrator to unit cries and laughter, and music. It improved on the first game's unit management, especially with regards to formations and pointing your troops in a certain direction. Outdoor levels received buildings and interactive pieces, and indoor levels were added (though they're arguably not as good as the wide-open outdoor levels). There really isn't much one could complain about Myth II, unless you're one of the folks who isn't completely happy unless you have a group of resource gathering units milling around and a base to micromanage. Micromanaging units is so much more fun, and causing complete bloody mayhem while doing so is even more fun.