~ Gheb ~
mind explaining why you feel that Fox's FSmash is notably better than Bowser Jr.'s? I do think Fox's is better but they do different things. Fox's covers ground and moves him forward to punish, whereas Bowser Jr.'s FSmash is large, disjointed, powerful, and has very low cooldown. Its biggest issue is its multihit natire, which often causes it to clank uselessly before the final hit. However, it's still a strong choice against aerial opponents and it's essentially safe on shield, remarkable for a move that strong. I wish it could break shields like it did in the trailer
I'm also curious why you feel that Sonic's FSmash is exceptional among the move type. It's good, one of the better FSmashes, but it doesn't feel like an S tier move. Its best attribute is being able to catch the two frame on the ledge (anyone know the frame its charge window starts on?) which is a very good thing. Outside of that, it's rather slow at frame 18 and does pretty poor damage. Decent cooldown also redeems it a little and makes it hard to punish.
Villager's FSmash, as much as I love it, is probably not S tier but A. Being able to drop it from ledges and platforms to hit those below him is great (and can nab some really early kills since it gets stronger after it falls a few frames). However, as a projectile, it can be clanked/beaten or reflected (if reflected from a far enough distance Villager can Pocket it though). Its projectile nature does have some plusses; once it begins to fall its hitbox exists independent of Villager's state. I've gotten numerous kills from FSmash still hitting despite me being hit. The move also has very low cooldown at 21 frames.
Game & Watch's FSmash is okay. It's a little slow and requires a sweetspot to get its good kill power. It is, however, his longest-reaching horizontal attack (I think, BAir may beat it) and is nicely disjointed. The diagonal angle he holds the torch out at can let it be a decent anti-air. Cooldown isn't too shabby at 25 frames. It's also his strongest punish for a shieldbreak if you don't have Oil Panic charged or don't want to risk a 9. Only hits for two frames, though, which is unfortunate (and illogical). B or C tier.
I feel that Pikachu's FSmash is being glossed over a little. It has 8 active frames, with the strongest being in the middle of the attack. It also has good range, especially for Pikachu's small hurtbox. Also worth noting is that its smash charge window is one frame before the hitbox comes out, allowing it to release very quickly. For all this its recovery is a respectable 27 frames. Probably A or B tier.