Spoilers are ok on any episode I've commented on, and I have a fair idea of stuff that happens later on but I'll ask for no spoiling specific stories unless directly asked to (i.e. no "episode X is when monster Y!" shows up, but "Yea, this one gets re-used in a later series," or "You'll see this again," is fine).
Going by episode-
1) Solid enough origin, but one thing kept bugging me during the episode: King Ghidorah. Namely, the phone ring of the science patrol sounds like King Ghidorah. No idea why, but when I'm in a kaiju mood my mind immediately went there.
2) Ahh, space alien! I think this is the best episode of the first 10, and really sells it as sort of an X-Files with giant monsters. Or Doctor Who with giant monsters, Strong plot, cool villain.
3-5) Various kaiju of the weeks. Often quite investigation based- something's up, gotta figure it out. 4's nuke-gimmick was fun but, ah, not all monster suits are winners. 3's Neronga is kind of silly and it underuses it's invisibility gimmick, and Ragon is way too human shaped.
6-7) Experimentations with genre! 6 deals with drug smugglers, 7 travels to elsewhere in the world. 7 is a stronger episode, but Ultraman was surprisingly kinda useless, not being the one to finish the monster. Antlar is a nice insect type design!
![Cool 8)](./images/smilies/icon_cool.gif)
9) Another kaiju of the week. Gabora is totally a Bulette! Looks cooler with the head closed.
10) Jirass! Aka the first Godzilla, of which I gather there's a few. And... yikes, Ultraman's actually pretty mean in this one, going for the frill and playing around! Pretty strong ep.
So far I'm noticing, the best episodes are ones with monsters I recognize. Which kinda makes sense- if I know them they likely got reused and referenced in other places, and if they got re-used, it's probably because they were good! Also naturally production would match the best stories with fitting, cool-looking monsters.
I'm also watching Redman, which is a really short show, pretty much lacks plot, and is more "Hero comes and murders random Kaiju," from the same era. No breakdown, because it's more just 'repeated kaiju fights'.