I've been playing through Knack 2, and IMO it is a dramatically better game than its predecessor. For one thing, the designers made an effort to finally rebalance the gameplay in favor of something akin to the LEGO games. In the first game, you died in 2-3 hits, no matter how many relics you had or where you were in the game. And when you got hit, that damage was persistent until you either found more relics, you hit the next area, or you died and respawned at the last checkpoint. Now, when you get hit, you lose a pile of relics & get smaller as usual, but if you can avoid damage for a few seconds, the relics fly back on and reattach, essentially giving you regenerating health.
The game also plays a lot more with alternating size & scale. Outside of the Stealth Knack sequences in the first game, you always started a stage small & progressed through the stage progressively growing larger. It lacked variety. Now, you can shrink back down to Little Knack at any time to fit through small holes & find secrets or to navigate puzzles.
Oh yeah, there are actual puzzles & platforming now. They're basic, but I find them satisfying enough.
You also have a skill tree of stat boosts & new moves you acquire by progressing through the story & finding XP crates.
So far, I'm about 1/3 of the way through the game, but I like it so far. I think Sony actually hit the "all ages cartoons platformer" mark they were aiming for, especially since you can play it local Co-Op. I'd recommend it for kids or the Young At Heart (TM).