Power consumption (the new models are down to 9 Watts now?) means games can be played non-stationary without a separate screen or power source. A running game is visually superior to a stationary console on standby.
Resolution (docked connected tv for like-to-like comparison): many multiplats and a few exclusives were capped lower than 720p, some into the 500s if we're talking PS3. I played those and enjoyed them, but the Switch outputs much better than those now.
Better AA capable than quincunx and other methods from that gen.
PBR being commonplace in current-gen games (remember when the Wii stood out as well as PBR was simulated in Super Mario Galaxy)
Far more consistent 30fps than PS3/360, some of those framerates last gen were inconsistent and sagging, but we still played and enjoyed them.
And this is kind of a "duh" answer, but some games have been remastered.
Now it's true, the Switch doesn't have a GTA or a Halo or a Destiny or a Uncharted or a Beyond Two Souls or a Ratchet and Clank. But it does have Warframe, Starlink (an eight-planet solar system total open world, which is all that No Man's Sky keeps accessible at one time anyways), NBA 2K (the full game, not cut down like other nintendo-version sports games), a Witcher, Rocket League, Diablo 3, Dragon Quest XI. Other games like The Outer Worlds and Gods and Monsters are coming. Establishing what is visually superior should be straightforward.