I kind of hate that everyone says oh don't watch the 03 version of fma because it has an unhappy ending. When really the 03 version with cos has a bittersweet ending. Take that into account first. Second, yes the ending is dark but it has hope in it. It has light. I feel like everyone constantly ignores the bit of light the 03 version ends with. Yes Ed and Al will face dark times ahead in a world that's not their own. But they will do it together. They were separated for a bit, but they managed to find each other again. Do you know how amazing that is? I think 03 teaches us that there will always be dark times, but as long as you have people, even one person to walk in the darkness with you can still keep moving, keep trying to make the world better.
Saying 03 is "sad" and thus "not worth watching" is very much a slap in the face to the very earnest message it is trying to convey — the world sucks, and things may not go the way you want, but this imperfect world is worth the fight, and closing yourself off when you're so connected to it, and it to you, is harmful and how things that "aren't supposed to happen" happen. 03 is a very rewarding experience because of the interwoven plotlines (shout-out to Ed's character growth as usual), and is 100% worth people's time and attention.
Beautiful point about the one person keeping you going <3 Ed & Al are so poignant, and the experience of witnessing the brothers' bond in 03 is unmatched. 03 is 100% worth all the pain and grief just for the feeling of fullness in your heart after you finish it.