Well, they "abandoned" Crash because Universal (or Activision Blizzard as they are now known) owned the IP, and ND only had a contract for three games, plus CTR. I'm not sure why they didn't renew it, because the Crash games were massive sellers, but they didn't.
So, now owned by Sony, they decided to try a new IP, and made Jak. It was never HUGELY successful, on the level that Crash was, but it did well enough. Sales decreased from one iteration to the next, so they tried something new again. And they got Uncharted. Slow opening, great legs. But it only hit 2.5 million. The second will destroy that total, and the third could sell more still. But apparently they are revisiting the Jak franchise after Uncharted 2, so they haven't forgotten about it.
The Uncharted franchise will be more successful than the Jak franchise in the end, and it's owned by Sony, so no problems there. We'll definitely be seeing it on PS4.
Also, Uncharted > Crash > Jak. But they're all awesome.
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