Seriously, you people give Showa Ghidorah WAY too much credit.
I personally think its the other way around. But whatever. Get back to me when Heisei Ghidorah destroys at least one planet, fights against at least three monsters at the same time, and destroy a city in less than a minute. Then
I might consider him being as powerful as the Showa version.
EDIT: Actually, while I'm at it. I'm just going to voice something that has been floating around in my head for a long time. I know the most of you will not agree with me, but I just want to give you guys something to think about.
Is Heisie Godzilla, really that more powerful than Showa?
Now stay with me on this. Sure, his beam must be more powerful. It does tend to make bigger explosions, but
that doesn't necessarily mean there is a gigantic gap in power difference. Think about Grand Ghidorah's beams against Rainbow Mothra. He was injured pretty easily. He travels back in time to fight Cretaceous Ghidorah, who's weapons have bigger explosions, and what happens? Well, she's hurt, but not as much as when she was struck by gravity bolts that caused smaller explosions. Now, I'm not saying that Showa Godzilla has a stronger ray, but is there really such a big difference in power? Or are we chalking a lot of stuff up to better special effects?
A big reason to why many see Heisei Godzilla to be more powerful is his durability. He went swimming under the mantle for crying out loud! But remember folks, Showa Godzilla has some pretty cool durability feats too. He took a cutter beam able to chop through a mountain, revolving missiles able to uproot entire city blocks, acid that makes Biollante's look safe in comparison, spider venom in the eye, (remember what a funnel web or black widow can do to a human.), toxic gas capable of melting steel, etc. Showa Godzilla's hide was breached in five films out of fifteen. Heisei's was breached in four out of seven. Showa seems to have a slightly better track record in the durability department. But heisei does have superior regeneration.
However, Showa Godzilla is faster, smarter, and has better T&C capabilities to Heisei. And they share roughly the same amount of strength. heist, of course, has a nuclear pulse, but how often does can he use that thing? Perhaps Heisei is stronger, or perhaps they really aren't that different in power after all. Each have their own strengths and weaknesses. It's always possible that Heisei Godzilla may be a little bit overrated, due to the powerful nature of the enemies he tends to fight and better special effects.
Just a thought.