Best and worst most extreme departures long running series have taken?

[curl-6]

Best: Fatal Frame: Mask of the Lunar Eclipse

The move to an over-the-shoulder camera and the introduction of the "touch" mechanic where you have to hold a button to reach out and pick up an item or draw back a curtain were both huge steps forward.

Worst: RE6

Not scary at all and riddled with all the worst cliches of that era from excessive quicktime events to being overly scripted.