Looking at your specs, it looks okay to play several games. Try trouble shooting, burn a Super Mario Galaxy iso at 3x.
By looking at the information you provided, it looks to be like a iso copying issue. Check Imgburn tutorial on burning in tab mode and check write, then lower the copying speed to 2.4 using the dvd-r mentioned above.
Other burners some say better then imgburn are:
**InfraRecorder for turning your backup wii game(dvd-r) back in to a .iso file,
you can also make a backup game (dvd-r) from your .iso with this program.
**This CloneDVD.v2.9.0.9is great i found for making (burning your .iso files to DVD-R) your wii games.
Both of these can be obtained in torrents. The later (clonedvd) needs a keygen.
try the trouble shoot i said above and let me know.
~aloha kawainahe
p.s. pls. give a thumb thanks if you get a chance