A lot of my all-time favorite games seem to be overlooked at the time, so there's not too many of them I can admit to being overrated. I remember thinking Xenoblade would fit this category...until I played it. Such an incredible game...easily my favorite RPG on the Wii/PS3/360/DS (didn't own a PSP).
I guess I'd probably have to go with Earthbound. I never played it back in the day, but when it came on the eShop, I wanted to see if there was a reason for the cult following. It's definitely fun, and has a lot of charm, but I found the actual gameplay to be really boring. I would run out of MP/TP (whatever it is in this game) so fast, I basically just stopped using anything other than regular attacks.
I still need to beat it. Just need to find that motivation...
NNID: Zephyr25 / PSN: Zephyr--25 / Switch: SW-4450-3680-7334
