Welcome, Kev!
"The Godfather Trilogy" was the chronological version of GF1/GF2 plus GF3. The originals from the early 90's are not numbered.

.
Don't confused that with "The Godfather Collection" that was also re-released in '97, which contains the 3 films separately (not chronologically), plus other goodies in the Limited Edition version:

There are more details
here...