For me, Rogue Leader is the best game of the whole 6th Generation, let alone best on Gamecube or best aside from Smash and Zelda.  Any game from the 6th gen that rivals it for me is because of the addition of motion/pointer controls in Wii ports elevating the experience like Prime 1 and RE4.  On the Cube those games are far below RL for me.

I lost interest in Nintendo during the N64 and GameCube generations, but the release of the Wii made me regain interest.  However, all Wii hardware was sold out after it released, so I bought a used GameCube in 2007.  I got a bunch of first party GameCube games on sale.  I think I only paid $20 for Fire Emblem.  Several years later I sold all of my GameCube games on Ebay.  I got around $90 for Fire Emblem, but I think it's worth a lot more than that now.