I also had a hard time getting into The Host at first, there was alot going on in the beginning that didn't make much sense the first time through the book. It seems to me that the problem was that you were being put into the story from the aliens point of view, barely arriving on earth, while you had no background knowledge of what was happening, there just wasn't much to relate to (How many of us are parasitic aliens?). Meanwhile in those first few pages of Twilight your seeing the new kid in high school, worrying about finding friends, classes, etc. which most everyone has had some experience with, so its much easier to relate to.
Honestly, lets say the first twilight book released was from Edwards point of view, how many people would relate to a vampire's struggle to not kill bella in the first chapters? I think most people would skip that book if they didn't have the backstory, because it would be just as alien as The Host is. (Of course now that you've read Twilight you want to get the other side of the story, but I'm pretty sure you wouldn't have liked starting with it).
Twilight was good because it was so easy to relate to, it had feelings that everyone has had, with alittle bit of mystery to intrigue you.
In The Host I liked the depth of the story, the dilemmas faced by most of the characters about trust, friendship, love, loyalty. It was just a very compelling story to me, the stuggle with right and wrong when the line was so blurred because of what Wanderer was.
I liked them both, and I wouldn't say one was better overall then the other, because they were both good to me for different reasons.