Cards like the above Cloudkin Seer, Mulldrifter, or ones that have to self-bounce to abuse, as they don't have abilities to merely flicker - such as Thornscape Battlemage
Rares and mythics have a hard time maintaining much value, since they are illegal for tournament play (and are probably barred by many casual playgroups as well)
Dragon typal has several dedicated ramp pieces like Dragonlord's Servant and Dragonspeaker Shaman that help get the job done
On top of that, collectors are also heavily speculating on whether high-rarity serialized cards from the upcoming MTG Marvel Super Heroes set will eventually crack this all-time list
That usually makes for a cleaner, more comfortable walk-through experience, especially for collectors planning to spend a few hours on the floor comparing inventory, making trades, and revisiting tables before deciding on a deal