well, i don't think i care for rose too much, Pearl feels kinda like a sheep to me, Garnet it probably my fave of the crystal gems and amethyst always felt a bit disconnected from the team. But i guess thats what i like about them.
I really like Garnet, Lapis and Peridot, all for different reasons.
I love Garnet's mother-like nature and overall maturity. I also love the way that she always encourages Steven and she takes better care of him that the other Gems. For example, when he thinks there's something in the warp stream, Garnet is the one who says they'll go check to ease his mind. And in Chille Tid, she insists he sleeps.
I love Lapis's design, plus the fact that there's so much drama around her. I love how she's devoted herself to keeping Jasper in the ocean.
I love Peridot because she's just so childish! When she doesn't get her way, she runs back to Homeworld and essentially "tells on you to mom." It's freakin' hilarious.
The favorite of my fusions (not counting Garnet) is Opal, though. She's strong, beautiful and genuinely cares for Steven.
I also kind of like the way Steven treats her. When the Injector falls on her, Steven asks "is she hurt?" This Gem who's trying to hurt Earth is still seen as innocent by Steven and I LOVE it. Steven's just a ball full of love.