I feel explaining the evolution of the Food Chain deck helps make it easier to understand why First Sliver is so good as the commander. First and foremost, he has 0 dead draws in the deck when built properly, meaning he has an insane density. To explain this, there are no other commander with 0 'dead draws' in the deck with Food Chain.

The first Food Chain commander was Prossh. Prossh however, is 3 colors and this limits his option considerably on what can be run, so an excessive number of slots have to be dedicated to subpar protection and outlets for the combo respectively. Prossh can also only run 2 of the 3 creatures that go infinite with Food Chain (other than himself when he is the commander). Prossh was the original Food Chain commander and can be run as his own Commander and not be completely wrong as it is a non-modular build and is a slow combo deck which is really beginning to fall into barely playable (which makes me a bit sad as he was my first cEDH deck). Prossh is a fun deck that is quite resilient, but is a bit slow for the current decks and there are several top tier deck he does not play well against. He also necessitates a high outlet density which is problematic at times.

Then came General Tazri the first 5 color FC commander. Her ability allowed for a modular approach as she could be used as an outlet, could run the best protection and removal, but required a few allies to be ran in the deck for her to work. Remove the allies, and she felt pretty awkward after the fact. She could run some very good protection, but her combo itself was pretty fragile despite being fast and consistent. Tazri could slot some recursion or back up ways of grabbing the other part of the FC outlets just in case as a back up, but this significantly lowered the threat density if she did.

Tazri for a while was still the best Food Chain deck you could run. However, she was eventually dethroned by Niv Mizzet Reborn. His ETB allowed for a few different lines, but the main way was to use Hydroid Krasis to draw the deck. Being in five color, he could run all the same cards as Tazri, and only required 1 other card to function as a true outlet for the combo. The deck could also run Corpse Knight or Circu, Dimir Lobotomist as outlets as well for the deck. Again, there are some light recursion lines to help in case of disruption. Overall though, his lines and interactions were better than Tazri as his ETB is more useful than Tazri's if you were desperate, and his cards to be the outlet were not completely dead without him or the combo (they weren't great but still better than Tazri's). Again, the modular approach allowed this deck to adapt from meta to meta well and remain threatening.

Then a month and a half later came the new, current, and unlikely to be dethroned king of Food Chain, First Sliver arrived and my god is he a beast for FC's commander. First Sliver is fantastic for Food Chain, as like his predecessors Tazri and Niv, the deck can be modular to adapt to the meta, but unlike his predecessors, he needs no help being the outlet. His deck is pure interaction, tutors, ramp, draw, and combos. First Sliver has the most busted effect you could want in Food Chain: Cascade. So what Food Chain only makes mana for creatures when your commander can cast your entire deck for you. Ad Nauseam is about the only card run in the deck that shares his cmc, and even then with the ability to repeatedly cast the deck who cares. Because he does not require any other cards, the deck can run several combo lines and win conditions so that the only real card that can be taken out with a card like Praetor's Grasp (if an opponent is even running it) is FC itself, and even then the deck has built in back up combos that let win anyway without FC. To summarize and make clear what I am saying: First Sliver converts infinite FC mana to the ability to cast your entire deck. This can turn into a Tainted Pact/Lab Man combo, Time Twister (or the budget equivalent) loop cards such as Extract and mill everyone out, or even midrange game plan because he runs no fluff pieces, he can run whatever he needs and wants to allow a grind match against control and just win when they get exhausted or leave an opening. This is what makes him so strong as the commander, First Sliver runs no fluff, can run several lines, back up recursion that does not slow him down at all, and can even use the back up recursion to win if need be.