I think a few must have PS2 games would be Ratchet and Clank 2, Jak 2/3, Metal Gear Solid 3, Sly Cooper, Kingdom Hearts 1, DMC 3, God of War 2, Silent Hill 2, Okami, and Resident Evil 4.
I still own my PS2 as well as all of my old consoles, however I haven't played any games on it for a while as it happens to be in storage. Luckily some of my favorite games (Ratchet and Clank, Jak and Daxter etc.) have been rereleased in HD so I can revisit the good times.
Just wanted to say I agree with cyber, I think having content focused on Dota and League would bring in more users, or give people who are fans of MOBA's something to talk about since they've been so popular as of late. Also they're really factoring into the e-sports scene in a large way and...