I think FRLG is the best Pokemon game ever (tied with Platinum and HGSS).
FRLG is not the most complete game in terms of content, because Emerald, Platinum, HGSS and BW2 all have more content than FRLG overall. But FRLG has some things that just make it special and unique. Like for example:
>Sevii Islands: an amazing island archipelago that cannot be experienced outside of FRLG
>Trainer Tower (there's a similar battle facility in Emerald called Trainer Hill, but it's not exactly the same, and FRLG's version is better)
>Fame Checker
>VS Seeker (shared with DPPt/BDSP)
>Trainer Card customization
>Selphy's requests
>Etc.
Furthermore, there's also something unique about FRLG's art style and visual presentation, that most other games lack. Wonderful details like the location preview feature, Teachy TV, the reminder of what you did before saving, etc. These are all things that enhance the overall game experience that we barely ever see in other Pokemon games.
But also, there are other more obvious reasons why I like FRLG so much: FRLG Red is my favorite player character design in the series, Charizard is my favorite starter, Kanto is one of my favorite regions, and I love the music too. I feel like all of these things combined create a fantastic experience for the player.

Thank you for reading, and please share your opinions about FRLG with me. Is it one of your favorite games too? Or do you have other favorites?

For me it's: FRLG = Platinum = HGSS > the rest