Most older FAT PS2s can't read cheap discs (Memorex is a very good example of a brand that makes low-quality discs) and DVD+R discs.
The odd thing here is that I tried a few of them on a friends fat ps2 and they worked just fine. I have NO idea what's going wrong here since I've done nothing differently than I did before and the games I burned previously work just fine. Any ideas?
Another possibility is that that set of Verbatim discs you've got isn't manufactured by Taiyo... but some cheaper company like CMC.
Stick to only Verbatim (Taiyo) DVD-R discs if your PS2 is one of those PS2s with the older KHS-400 lasers.
A really close situation to what you've experienced: My 39001 PS2 (Before I swapped it for my 39006) couldn't read any of the discs my 39006 can read (Except for those Verbatim discs).
SCPH-10000 S. MINOKAMO v1.01 (Defunct)
SCPH-10000 S. KISARAZU v1.00 (faulty)
SCPH-15000 S. KOHDA (With warranty seal!) :D
DESR-5100 S. EMCS