I started typing out a reply saying that the PSP sold more than the 3DS, but then I realized it's actually kinda hard to measure how the 3DS performed against the PSP. Here's why:
- The 3DS has currently sold around 60 million units to consumers worldwide as of the end of this year. This number was achieved over a 5-year period. The split is even between regions: 22 million in the Japan, 20 million in the US, and 20 million in the rest of the world.
- The PSP has supposedly sold somewhere between 70 and 76 million units, but a) that's the sell-in number, i.e. sold-to-distributors, b) it was achieved over an 8-year period (it had sold 51 million units by 2009, i.e. 10 million less than the 3DS in 5 years), c) I can't find official sales figures per-region. The last official update on regional sales figures had the exact same split as the 3DS: around 20 million in each region.
Given all that, it's reasonable to assume that the 3DS and PSP performed in the same ballpark, and that whatever edge the PSP had was due to its longer lifecycle, sell-in figures/vs. sell-through, and maybe one region performing better than the others. If anyone has more up-to-date figures, I'll take them.
Make no mistake: yes, the 3DS is Nintendo's worst-selling handheld (the GBA is at 80 million), and yes, the 3DS is definitely a failure given all the hype it had leading up to its launch and coming from the record-breaking DS. Likewise, the PSP was a failure because Sony and everyone else expected it to take the world by storm and wipe the floor with the DS. But no system that sells 60+ million units is a failure, unless that's literally 10 times less than the previous generations or than the competitors.