While video game graphics have grown more powerful over time with the inexorable march of technological progress, there's something to be said for graphical impact relative to a console's time period; of the systems you have owned, which felt the most powerful at the time to you, and why do you think this was the case?

Super Nintendo. Mode 7. Then FX Chip. So Stuff like F-Zero and Pilot Wings on launch. To Donkey Kong Country and Starfox. It just made Genesis look pitiful. Even tho Genesis could put out some amazing looking stuff at the time.  Mode 7 was just magic back then and sprite scaling. Super Castlevania IV rotating tunnel.  Yes Neo Geo was the most powerful console of the time but few knew of it. To most kids it was just SNES vs Genesis. 

N64 and Dreamcast had that effect for me. N64 for its ability to standardize the 3D dream (SM64) and Dreamcast for its ability to fulfill it. Everything after felt more incremental.

PS2 in 2001. Gran Turismo 3, MGS2, Ace Combat 4, Silent Hill 2, and Tekken Tag looked unbelievable. Also Resident Evil Remake on GameCube looked absolutely ridiculous, It's just hard to believe today that RE1 and the Remake were just 6 years apart! The character models blended well with the hyper realistic prerendered backgrounds on a CRT.

FM Towns Marty.

It was backwards compatible with FM Towns games, and it could run Puyo Puyo.

SNES. Yeah, they kind of skimped on the CPU, but the other hardware more than made up for it, at least for the kind of games I enjoy.

N64. Its best 3-D games looked better than anything the PS1 or Saturn could put out. A lot of the best-looking PS1 games relied on pre-rendered graphics to look good. It had its deficiencies, brought on by its cartridge format and memory bottlenecks, but the Zeldas and some of the Rare games were amazing.

The Bally Astrocade. At the time, it looked as close to having a home arcade as you could get.

Gamecube. I guess I'm saying that as somebody who never had an Xbox, but Resident Evil 4, Twilight Princess, Metroid Prime, and Wind Waker looked incredible, and they have not been able to successfully re-create the 60 FPS gameplay of Tales of Symphonia in any of the remakes that were derived from the PS2 version.

Super Nintendo.

Mode 7 for sprite scaling and SuperFX for even better effects and even 3D graphics rendering capability.
Combine that with vastly superior audio capabilities and the Super Nintendo was a treat for the senses.

...But still no match for something like the Neo Geo or what the PC was delivering,

Cheeky answer for me, but PC. I was all about the ps5 and thought it was putting out some great looking games.. till I built a PC and started playing 120 fps, 4k DLSS and high/max/ultra settings.

Prior to my PC build, I would have went N64, because it simply could do gameplay things the ps1 couldn't. DC was the first console where I was shocked at realism.

Xbox og.. play doa3 or doaxbv those graphics where insane

PSP. When that thing arrived it felt like having the power of a stationary console in the hands. It played movies and music and stuff as well. The GBA could play games that looked like SNES games and and DS could play games that looked like N64 games. In my mind that felt like a natural improvement in the handheld space. But here comes the PSP skipping a whole generation playing PS2 level games. That felt like real power in a pocket.