Yes, this thread is everywhere, but it's fun... and heck, it's Metroid! You know what to do, make a boss that you would enjoy fighting (and preferably everyone else would enjoy fighting, as well), or just comment on other people's ideas.
My idea for a fun boss would be a gigantic armored turtle that floated back and forth over a huge lava pit. You would have to defeat it by shooting missles downwards at the bug... but you have to stay in midair constantly, since touching the lava would mean a quick death. This boss would give you the Gravity Suit, and I assume you would have the Space Jump already. The boss would die quickly, but it would do a lot of damage, make the battle quick but challenging. After beating the boss, you would get the gravity suit (probably from an X parasite), fall through the lava, and move on.
I actually had 2 ideas for Ridley a while ago.
1. Ridley stays on the ground. Attacks be normal means, as well as lunging and slashing.
2. Somewhat similar to GM's idea, Ridley is fought on a platform floating on some lava. After dealing enough damage, Ridley goes berserk and starts tearing the place apart, causing a Chozo Statue to fall through the ceiling, which contains the Gravity Suit. Ridley then destroys the platform and the rest of the battle takes place in the lava.
I'd go into more detail with these, but there's that thing called 'laziness'.
Mine had no platform at all. You literally have to keep space jumping and shooting downwards.
I would have a boss where you have to run and set up all these traps to slow the boss down from chasing you. Then you reach an area where you and the boss freefall for a while, so you are fighting in the air.
Not really a boss design, more of a what happens while fighitng it design.
I wish NST used more creative bosses.
What if, you know, somehow Samus fused with Ridley because of her special Metroid powers and the Federation made this big robotic Mother Brain and you got to control Ridley and they have this big battle and everything blows up except for Samus because she escaped into her ship at the last second like she usually does?
It could happen.