I don't think any TV show ends up making a good movie. It was TV series for a reason. If it would make a good movie, then it was a horrible TV show. TV shows are designed to tell much larger stories than a movie or 3 would allow them too. They are much richer than any movie story because of the amount of time they can devote to a plot. If you are able to remake a TV series into a decent trilogy, then there was a lot of fluff in that series and it really didn't need to be a TV show to begin with.
The first season of Lost was amazing. After that, it was a lot of fluff. Personally, I'm a fan of what American Horror Story is doing. They have a story that would be too long for a movie, but too little for a full length, multi-season TV series. 1 Season, 1 story. There are many TV shows I felt would have been better as mini-series like these. I'd like to see more shows like this. If they want to remake TV series then I think this is the route to go.
Purely for budgetary reasons, some shows could have looked better with movie money. There is nothing worse than a great TV show ruined by poor CGI work. I think with the growing popularity of TV shows lately, we could start to see some bigger budgets for FX and other things that might have only been available to big budget movies previously.