Lovely work as always, Iveechan. It's especially fun to see the fakes I remember from yeeeeears ago, heh.
About the Fire starters, what is the second one's pose supposed to be exactly? It's like it's somehow rearing on its hind legs while still completely horizontal, which doesn't seem to make any sense - in any case neither foreleg seems to touch the ground.
I think the third one would probably look better with flames only on the front paws; right now the bottom of the sprite looks a bit too busy and one might not even notice at first glance that the fire is actually on the paws rather than just all around it. I also don't really like the look of that topmost flame, which feels too regular in shape (it's the part where there is a large flame coming out at the top of the foreleg flames that just has a red outline, an orange middle, and a regularly shaped yellow center, rather than the little chaotic irregularities you have in the rest of the fire). I also notice there that the entire tail is outlined with the same color - might want to use some outline shading there. I really like that one, though - if I were picking a starter in this game, I'd probably pick it.
As for the Water starters, I actually think the first one looks the worst of them. The pose is rather bland and the flippers kind of stiff and the shading just kind of bugs me. On the near flipper, for instance, you're making it look extremely round, when a flipper would more sensibly be a kind of flat shape. In order for it to look that way, you'd need to restrict the shadow to what would be the actual underside of the flipper. Additionally, that highlight right now faces the right, which doesn't work with the universally top left light source of Pokémon battle sprites. Likewise, the shading on the back bothers me, with that highlight in the middle of it not doing a very good job of portraying the shape of the back. Since the light source is in the top left, there should be more light towards the tail, where it's facing towards the top left, than on the neck side, where it's facing more towards the top right. On the belly you then make it look like the light source is directly on the left, with the highlighting going way down to where the light shouldn't reach. I also agree with the previous comment about how the emphasized separation between the body and head is not really appropriate to an aquatic mammal.
The second one is my favorite. I agree the markings would look more symmetrical if you added more white to the far flipper, covering what we see of the thumb, for instance. The highlight on the head should probably be bigger in my opinion to portray the shape of the head more fully: since you're not using the shadow color there, you should use the highlighting color to fill everything that faces towards the light source. On the belly you have a highlight that's facing a bit down and in fact touches the shadow, which doesn't make sense. Then the dorsal fin, thanks to the shading, has that same problem of looking too rounded when it should be a pretty flat surface; I recommend cutting down on the "shape-based" shading and focusing more on the shadow that falls on the fin because its head is in the way of the light. It could also look more attached to the body if you got rid of the outline between it and the body, instead just letting the shading separate it from the back. The tail flippers should have more symmetrical white spots, and the far one has too much highlighting compared to the near one, making it look like it is actually lighter in color. I also think you would be better off making at least a bit of a gap in the outline in front of the far tail flipper, to make it look more attached.
I actually don't think the third one is too cute; what makes it perhaps look that way to some is just that, yes, it is rather oddly rounded, particularly the hands. By the way, I actually really like the fact it grows hind flippers and then full-fledged legs. Since when did Pokémon have to look like strict adaptations of one particular real-world animal? However, I'm also a bit confused about your intentions with the limbs on the last one. It seems like you're making them a bit like fingered/toed flippers, sort of floppy while being shaped into quasi-digits, but I think this could be part of the "roundedness" problem - it's got sharp teeth, and you've got it posed like some sort of a bipedal mammal or reptile, so my mind sort of expects to see claws on it. Again, Pokémon has no qualms about shamelessly mixing completely different animals together (just look at Scyther), so I wouldn't consider that a problem in the least. If, however, having flippers with quasi-digits rather than full-on paws is an integral part of your design, I won't hold that against you - perhaps try shading them more effectively to portray the shape better?
Anyway, the dorsal fin should definitely be lower on the back - remember, on a real orca the dorsal fin is considerably lower on the back than the flippers, for instance, while your Pokémon has the dorsal fin way up between the shoulder blades, almost on the neck. It also has the same problem as the second one's dorsal fin, with being shaded like it's a lot more rounded than it ought to be. I also agree that the pose looks a bit painful - you should probably raise the head higher up, especially since if you move the dorsal fin lower, that won't cause it to no longer fit into the frame if that's what you were worried about.
Finally, concerning the icons, I really wouldn't recommend going with the ones you have now - I mean, if you're going to put them into a FireRed hack, they'll look extremely out of place in the party next to the shaded top-down-view icons for the other Pokémon. The top-down view isn't as hard as it feels the first time you attempt it, really; it's good to look at some of the official icons for reference for how things are placed and what the perspective does to the body, and then you pretty much get hang of it quickly. They really don't take much more than ten or fifteen minutes to make at the most, shading, animation and all.