Great podcast!
I think that Lord of the Rings would be a stellar Lego game.
The Metal Gear Solid series was also the most creative suggestion IMHO.

While listening I thought that the following franchises might work well with Lego branding and gameplay:
Lego Fallout
Lego Thief (although, like Metal Gear series, stealth gameplay might not work so well in Lego world.)
Why not take Lego Star Wars or Batman and add an MMO aspect to it?
Lego Resident Evil