So my Xbox 360 gone to get fixed and I’m stuck with my original Xbox my question to use is out of these games on the original Xbox which do you think you would spend the most time on?
If I had my original Xbox, I would play Halo 2’s campaign and play Godzilla save the earth on it all the time.
Halo 2.
All day, everyday.
But out of your choices I would choose republic commando.
Halo 2 
Get xbox connect and play halo 2 online,if you the patience enough to find a game.use this website http://www.xbconnect.com/ they have all the tutorials and moderators there if you need help.
Republic Commando
Definitely Halo 2.
Star Wars Battlefront 2, if you’ve never played it you are missing out, unless you get it on PC
Halo:CE, since it was the only 1st gen xbox game i kept lol.Mostly because i absolutely love CE, and i still enjoy it even while play it on the 360.
Edit:Out of the limited options you gave, i guess Republic Commando is the lesser evil.So i would play that.
I loved Return of the King a lot.
But I would also play Def jam Fight for New York. I was hooked to that game.