While the original Godzilla film from 1954 is probably the best of the series in terms of being a piece of serious (for the time) cinema that serves as a fascinating look at Japanese society's attempt to cope with the trauma of Hiroshima and Nagasaki and the Cold Wars arms race, it's not my favourite of the series as I feel some of its successors are more enjoyable as escapist entertainment.
The 2001, 2014, 2016, and 2019 films I find more fun.