I can't say much about what I think about Legacy games without some spoilers, so here we go:
Spoilers for Risk Legacy and Pandemic Legacy:
I like the idea of Legacy games in theory, but one thing I absolutely require is that you still have a playable game after the campaign is over. This is what my group enjoyed about Risk Legacy. After the campaign is all said and done, we have our very own unique Risk board, but one that can still be played indefinitely into the future if we want. This is why we passed on Pandemic Legacy, because it was spoiled that the game renders itself basically unplayable after the events of December. ---