It's all rather subjective. Or rather, it's just conditioning. Personally, you can't beat a good SDTV CRT set with
any Plasma or LCD or even high res HD CRT set for retro game systems. Not saying it can't look decent, but that's not the same thing. No beautiful analog filtering and low res dot pitch mask and scanlines gaps and all the other analog goodies. Even the beam on the scanline itself, has hit beautiful vertical fade on the top and bottom edges. It's super slight, but it means the scanline isn't perfectly square and flat like on a LCD or even RGB monitor. That said I'd never play a newer gen system on an old CRT, starting with the PS2 era.
I've read that most digital displays have a hard time with the Genesis composite output. There's no alternating chroma dot pattern (like snes/tg16,etc), so it's harder to pull detail out of the signal.
Funny, 'cause a lot of the LCD tvs nowadays have filter overload. It's all about 'smoothness'. Both 2D and now temporal. I dislike both, but especially hate the temporal motion expanding filters. I turned it off on my brothers TV when he wasn't looking
I also completely agree with how bad unfiltered pixels look on a large display (50+). My HD set particularly has an incredible composite and svideo decoder. The pixels are incredibly squared like it was being from a superior signal. That said, it makes my Saturn games look like ass. No good. The lack of scanlines makes me sad too. I have a 53" HD Hitachi CRT (biggest RP CRTs they made). For playing 4:3 retro stuff, it's equivalent to having a 70" wide screen with lettering boxing on the size. So you can imagine, the pixels for old systems are LARGE.