I'd watch in order of length personally, so start with Steins;Gate (24 episodes + 1 OVA + 1 movie), then Code Geass (50 episodes), and then FMAB (64 episodes).
Going over them, Steins;Gate is my favorite anime of all time. Best time-travel storyline I've seen anywhere, and the twists and WTF moments are too many to count. The first half sets up the whole thriller plot in the second, but it has its intense moments, too. Characters are all great in their own right and the lead is one of the best in recent memory, both for how likable he is and how well-written he is overall (I strongly recommend the dub, because he is so much better with all the hammy dialogue he's given there).
Code Geass isn't a favorite and I haven't watched it since I finished the first go-around, but I do respect it for its audience scope and deep and complex plot. I don't consider any of the characters among the greats (Lelouch is close, but I'm still skeptical about all the hype he gets), but most of them are memorable and well-written, and it's got plenty of epic battle scenes with fitting music. Prepare to have your heart broken more than a few times before it's over.
Brotherhood WAS in my Top 15 until a handful of other series pushed it out, but I easily support all the appraisal it gets compared to Geass. Easily the best shōnen series out there with tons of memorable and great characters and villains, with strong action and visuals, and both hilarious comedy and heartwrenching moments. Shouldn't really spoil anything given its genre, so I guess it's safe to say it's also one of the most satisfying finales I've seen for any anime series.
Going over them, Steins;Gate is my favorite anime of all time. Best time-travel storyline I've seen anywhere, and the twists and WTF moments are too many to count. The first half sets up the whole thriller plot in the second, but it has its intense moments, too. Characters are all great in their own right and the lead is one of the best in recent memory, both for how likable he is and how well-written he is overall (I strongly recommend the dub, because he is so much better with all the hammy dialogue he's given there).
Code Geass isn't a favorite and I haven't watched it since I finished the first go-around, but I do respect it for its audience scope and deep and complex plot. I don't consider any of the characters among the greats (Lelouch is close, but I'm still skeptical about all the hype he gets), but most of them are memorable and well-written, and it's got plenty of epic battle scenes with fitting music. Prepare to have your heart broken more than a few times before it's over.
Brotherhood WAS in my Top 15 until a handful of other series pushed it out, but I easily support all the appraisal it gets compared to Geass. Easily the best shōnen series out there with tons of memorable and great characters and villains, with strong action and visuals, and both hilarious comedy and heartwrenching moments. Shouldn't really spoil anything given its genre, so I guess it's safe to say it's also one of the most satisfying finales I've seen for any anime series.