I totally agree. MOHAA and HL were good games, but very linear. Deus Ex was quite good, but the best game IMHO has to be Morrowind. The main plot may be fairly linear, as there are basically only 2 ways to finish the main quest, but you are free to go wherever you wish to go. You can join any guild you like, but every action has it's consequences. Morrowind is by far the most interactive game I have played so far.