Party. Mass Effect forces you to take 2 companions at all times, while Ultima 7 will allow you to take anywhere from 0 to 7 companions, at your choice.
Inventory. Mass Effect allows you to choose the gun you use and little else. Ultima 7 has a full inventory for all 8 characters.
Trade/Merchants. Mass Effect has credits which allow you to buy...guns? (Anything else? I forget) While there is no shortage of money in Ultima 7, there are many shops and many things to buy; weapons, armour, vehicles, spells, food, and miscellaneous crap, as well as some interesting ways to make money.
Exploration. Mass Effect offers you missions to be approached in a varying order, but forces you into following small linear routes in mostly empty maps. Ultima 7 has a fully open world with traditional RPG things like traps, switches, teleporting etc., i.e. classical RPG dungeon type things.
World Interactivity. Mass Effect has no world interaction of any kind. Everyone knows of the interactivity of the Ultima 7 world. Interactivity that can be used to your advantage to affect the game in many ways (some listed below). I'm not doing a full list.
Non-scripted problem solving. Mass Effect offers only the ability to shoot things in the environment or sometimes talk to them. There is nothing else. While there is no alternative solution scripted at any point in U7 (AFAIK), the open world mechanics enable some creative solutions to be employed (potions, retaliation between NPCs, crate/object stacking, locked doors, collateral damage, serpent venom, NPC spell casting etc.).
that's cool and mostly true, but none of those are rpg mechanics, and as i already said, it was a rather excellent sandbox and a good adventure but rpg mechanics are the heart and core of everything remotely rpg. you cannot have a good rpg while neglecting them, and at least for me, the very best rpg evar would have to implement them perfectly, meaning they apply to everyone and everything in the world, which means, amongst other things, that they flow into every subsystem/all forms of interaction, not just combat. both mass effect and ultima fail badly in that regard, but ultima does more so than mass effect since me at least has barebones social skills, while in ultima the mechanics do not affect anything outside of combat. when items are hidden, they are hidden below stacks of other items or behind some wall that makes the item near impossible to notice. there is zero influence of your character build (well, technically there isn't really much of a character build anyways) over that system, or any other.
the non-scripted problem solving would be nice for an rpg if your stats had anything to do with it, rather than it all depending on you dragging items around to abuse the engine to make stairs, or abuse the lame ai by placing items it cannot even pick up to block doors that are supposed to close on scheduled times and whatnot.
it's a cool sandbox feature, rpg not so much.