Yes, I've got Rolemaster on my mind. What can I say? I like the rules, I like the overall system. What's good about it? Well, this is something me and my friends discussed when we first started playing.
First of all, RM came out back when there mainly only AD&D 1E, then the second edition, and other early fantasy role playing games. For the most part a character, like a fighter, seemed like any other fighter. There were very few differences, especially in the first few levels. That can't be said of a Rolemaster character. You might create a fighter, but with all the options and skills he's going to be unlike someone else's fighter. The fighter will be unique. Especially in the Rolemaster Standard System, and the next edition Rolemaster Fantasy Role Playing.
You aren't limited in the skills you can learn. If a fighter wants to learn to pick locks he can. It's going to cost him more development points ( skill points ), and he won't be able to learn as fast as a thief or rogue, but he isn't prevented from learning the skill. A fighter could also learn certain spell lists if he wanted. Again, it's going to be difficult, but it's possible.
Add in talents, flaws, background options, etc. you can really customise a unique character.
Combat is always unique as well. No two combats will seem the same. I think that's a real strong point of the system. Combat has many options, it's not just a swing and hit or miss. You can remain in a strictly defensive mode, or go all out on offense. Or mix and match as you see fit. Want to try something different, an unusual maneuver to surprise your foe? Go right ahead, it's covered in the rules.
I don't want to go into a lot of detail but there is a rich variety of spells. There are plenty to choose from.
As your character gains experience he can buy new skills, get better with his weapons, and can even have his characteristics ( stats ) get better, or even worse! Leveling up can be an adventure all on it's own.
Speaking of experience it's handled in a fairly unique manner. The first time you fight a monster you get more experience points for defeating it, than subsequent fights with the same monster type. After fighting dozens of orcs you don't get the same amount of experience as you did when you first fought one. You also get experience points for good ideas.
Creating a character for RM can be a slow process, but I think the results are worth it.