Well, Tetris Party is exactly 1200 points and has endless replay value with a strong online mode (even though the online rankings are totally borked). But I have a feeling that's not the type of "long...ish game" you are looking for.
Picking up two of the excellent Bit.Trip games (I'd pick Void and Beat, personally) is another good way to spend all 1200 points. The games are fairly short but quite difficult - so you'll need to practice quite a bit to finish them and play even more if you want to master the high score list.
After those recommendations, I'd look at something from this list:
- Swords & Soldiers
- Mega Man 9/10
- Military Madness
If you want really long games, you might be better off looking at more of the Virtual Console offerings. There are dozens of incredible games that would last longer than any WiiWare title because they were designed as blockbusters when first released.