what is the best godzilla movie
There are several types of second best Godzilla movies. 1954 is without a doubt the strongest piece of media in the franchise and is one of the most smartly cynical movies I've ever seen. However, 1954's not a great movie to inform your opinion on the overall franchise; the majority of the series going forward is comprised of monsters beating the piss out of each other instead of solemn meditations.
If you find 1954 great and you only want to see serious takes (or if you're a fan of Evangelion), then the recently released Shin Godzilla is the next best thing. It's smart and chilling at times (though there's a reason it's not number one). Additionally, if dated effects were something keeping you from 1954, Shin Godzilla might bump up to your number one spot.
On the other hand, should you want to get crazy and watch some monsters make each other bleed, I'd recommend Godzilla vs. Biollante as the best one. It's not only really good as far as Godzilla movies go, but it also serves as an intro point for the Heisei series. These films share a pretty consistent continuity so if you find yourself enjoying it, you can keep moving and complete that continuity (which extends for the next five movies).