I personally think both Super Mario Sunshine and Luigi's Mansion are hugely underrated games, but no more so than Luigi's Mansion. Personally I'd like to see a new one developed on the Wii with maybe a co-op mode or multiplayer element in it? Even if they made some sort of Luigi's Mansion 3DS I would be rather stoked or even release it for WiiWare.
What do you say Technadians?
Do you want to see this face again?
Dude... 3DS... EFF YES YOU GET A BSB STAMP OF APPROVAL.
Shigeru Miyamoto even said that he would absolutely love making a sequel to Luigi's Mansion. So there is hope yet for us fans!
A Luigi's Mansion 2 would be pretty epic if I say so myself.