If you measure overrated as a ratio normalized to the actual quality of the franchise then Twilight would be more overrated.

For example:

Twilight quality = 0.3

Twilight overrating = 500

Twilight ratio = 1667

But,

Star Wars quality = 1138

Star Wars overrating = 3720

Star Wars ratio = 3.27

On a pure scale Star Wars is the most overrated (or most popular) franchise, but on the normalized scale some crap like Twilight could be considered as more overrated. But let's remember SW is far more universally popular. Most people hate Twilight, there's just a small niche market (10-16 year old girls, 44-55 year old women) that love it.