It also gets a bit more complicated when you factor in that there are two major widescreen formats:
1.85:1
2.35:1 (anamorphic widescreen)
You might have noticed that action films such as Spider-Man have a much wider screen ratio than comedies such as Wedding Singer. That's why even when looking at beautiful widescreen TVs there will still be black bars on some films because not all films have the same aspect ratio.