Microsoft Game Corp.
After Halo 3 there was halo wars, halo 3 ODST, and Halo reach. A new company (not Bungie) will be making a Halo 4 and rumor has it there will be a remake of Halo Combat Evolved.
Bungie
the company looked and Halo:reach is the best.
The game franchise Halo is owned by Gamespot, a popular gaming website. Gamespot is the owner of the Halo franchise, it is. It is the owner of Halo 3 and 4.
In some cases they are. It depends what company makes them. If they were both made by the same company they are probably the same size.
Halo 3 is so fun because the game company that created Halo, Bungie, received mass amounts of funding from Microsoft to make Halo 3, therefore it ended up having so many fun extra things (forge, theater, file share).
halo 3 obviously
Halo 3: ODST is the newest of the two, but not the newest Halo game.
The halo time line goes Halo Wars, Halo: Reach, Halo:CE (halo 1), Halo 2, Halo: ODST, Halo 3. Halo 3 and ODST are practically at the same time.
Halo rights are owned by Bungee. Technically Halo 4 is "Halo ODST"
Halo 3 ODST is not for PC but Halo 1 and maybe Halo 2-3 are
it goes halo, halo 2, halo 3, halo 3 odst and soon halo reach will be available