"We all want to watch TV."
For the specific sentence both terms could be used but they would have different meanings if you use 要 vs. 想. My understanding is that 要 implies someone/ones who wants to do something or needs to do something and will follow through with the action. Whereas 想 implies someone/ones who are thinking about doing something, a desire or feeling only. Here is a good video on it - www.youtube.com/watch?v=vb8BPhOohHs