The SNES is a wonderful system for RPGs. Here are a few of my favorites:
Secret of Mana: This is one of my favorite games of all time. It's an action RPG in which up to three people can play if you have a multi-tap. If not, you can get by with just two players or go on the adventure yourself. The AI settings for the computer controlled characters are fantastic. Other games that use AI settings could have learned a thing or two from it. The action is fast, but not button-mashy. The story sometimes takes a back seat, but there is still a huge world to explore littered with secrets. This gets my top recommendation.
Breath of Fire: This was my first RPG and I still enjoy going back to it from time to time. It has traditional, turn-based combat, a huge cast of characters, lots of dragons and an easy difficulty in case you're looking for something a bit more relaxed. Breath of Fire II has a better story and better graphics, but the game fumbles in much more areas. It's my least favorite in the series.
Chrono Trigger: An interesting story, swift battles, a great score and lovely graphics. Aside from some hideous Toriyama artwork, this game is flawless and has so much to offer. Chrono Trigger has some of the best pacing I have ever seen in an RPG. I won't get into the details because of spoilers, but the game starts with a bang and that momentum keeps up throughout the quest.
Lufia II: Rise of the Sinistrals: I finished this game for the first time about a year ago. Despite having gone through countless RPGs on other consoles, Lufia II still has more believable characters, better battles and features (IP is wonderful) and more content. It's a great game; I regret waiting so long to play it.
There are a few honorable mentions I can list, too.
Soul Blazer: An addictive action RPG that will sink its claws into you and not let go until the ending credits.
Illusion of Gaia: A follow up to Soul Blazer, but with a longer campaign and a more familiar setting. It's a shame the NA version got hit by so much censorship.
Final Fantasies IV, V, and VI: You can't go wrong with these games. Each one will last a good 30 to 50 hours, depending on how much you do. FFV can be played with an English patch.
Mario RPG: This is a "feel good" RPG with a battle system that has more depth than meets the eye.
Finally, if you're willing to patch and/or import, here are some great Super Famicom titles that never got the chance to see the west.
Secret of Mana 2: Ye gods I love this game. I'm still bitter about it never showing up here.
Tales of Phantasia: Compared to modern Tales titles, the series has come a long way. Still, there is something undeniable charming about this one.
Romancing SaGa 3: If you're looking for something non-traditional that lets you play without handholding, then consider this one.