so i was doing some research , and i found out that the Showa era actually ended in '89, so then that would make Godzilla 1984 the final showa film. what are your thoughts on this.

To me, it belongs more in a seperate catergory along with Gojira and GRA. To me these 3 films are similar in that they don't have the campy, fun atmosphere that most Showa (and GFW for some reason) films have. I would group it more in iwth Hesei fims.

Yes, technically the Showa era in Japan did end in 1989, but I think (at least when I talk about it) the Showa era in Japan and the "Showa" Godzilla era are similar but different. I've been like fans when I categorize the Showa films as 1954-1975 and then the Heisei as 1984-1995. Godzilla 1984 is way too modern and serious to be a Showa film for me. It's amazing there are less than 10 years seperating "Terror of MechaGodzilla" and Godzilla 1984. If you compare those two, they don't belong in the same category.
Obviously, Gojira and GRA are also serious but Godzilla 1984 will always begin the Heisei era and end the Showa.
Toho actually avoids calling them the "Heisei" films and calls them the "Vs. Series."

I hope this doesn't mean that you have to rearrange your shelves Ghido.

Ghido is correct. The Heisei era began in 1989. The Heisei Godzilla series began in 1984.

I actually enjoy doing that. Nice try, though.

If the Showa era ended in 89' wouldn't that make Godzilla Vs Biollante the last of the series?

As it was already pointed out, Emperor Hirohito died in 89, but the Heisei series of Godzilla films had already begun, even though there were 17 Godzilla films made in the actual Showa era.