It's not exactly on the top of my wanted sequels list, but I've always wondered why they never made a Pokemon Snap 2. I thought the first Pokemon Snap was fun and I remember it being quite popular back in the day. To me, it also felt a bit experimental and unfinished (with only 6 courses and half of the first gen Pokemon in them).
I wondered why they couldn't make a sequel that featured all the first gen Pokemon (and perhaps the second gen), with more courses and perhaps some semi-free roaming options. I'm sure it would've sold.