Bear in mind updates of both titles have been announced (damn you, Sega). PSO Collection + for the Cube will come out by the end of this month, and Sonic Mega Collection + for the PS2 will come out in a few months too.
The PSO collection for the PS2 is supposed to retail for for 20. Any deals for it will probably not show up for a while since it does not ship for another two months according to EB games.
The Sonic collection, I would wait and see. Even though the game list is really good, from what I heard the emulation was horrible (what people at E3 said, so I would wait for an update to come in regards to the quality of emulation)
idk, but Phantasy Star sounds great since i've never played it. and i love Sonic. in fact, last night i ordered Sonic, Sonic 2, Sonic 3, and Sonic and Knuckles, along with Mortal Kombat and Batman Forever.