Stanley RichardsDepends on the game you're playing.Water types are the [preferred] starters if you want an easy playthrough
Grass types for normal
and Fire types for a little challenge.
That too depends on the game you're playing.
In the first gen, Grass is easiest to start with, having super-effective damage against Rock and Water types, as well as being resistant to Electric for the third gym, as well as having an easy time with the 4th gym, Erika's in Celadon. It isn't until the 6th and 7th gym that you start running into problems. That dual typing with Poison screws you royally against Sabrina. The last gym is pretty much a cakewalk provided that you don't get hit with a ground move.
Water is balanced in the first gen, being able to handle the first two gyms easily, but suffering against the 3rd and 4th gyms. It is neutral in the 6th (Sabrina's) and very useful in the 7th and 8th. Having access to Surf and Ice Beam makes it a very good starter.
Fire struggles in the first two gyms, but is relatively neutral in the 3rd, 5th, and 6th gyms. It isn't until Celadon that you see some true firepower, and Blaine's gym being immune to burns and resistant to fire. The last gym is sort of a problem if you don't have a Gyarados or something similar by then. Because it gains a Flying type, it SHOULD be immune to Ground moves, but I'm not sure if they implemented that in the first gen for Charizard. It wasn't until Yellow that he was able to learn Fly, but as for immunity, I'm not too sure about that.
Second gen, the types are all switched around for difficulty.
Grass had a big disadvantage in the first two gyms, Flying and Bug, and suffered resistance against Ghost/Poison in the 4th, owned in the 7th, and relatively neutral in the rest of the gyms. Paralysis is still a problem despite resistance to Electric. Grass overall doesn't have a type advantage throughout the game, making this one the hardest of the three.
Water remained neutral throughout the game and is probably your best bet as being the easiest of them all, having access not only to Waterfall but Ice Punch as well making the 8th gym the only problematic one. I'd also say with Ice Punch, Lance is a BREEZE. The problem with Feraligatr is that Gyarados fulfills his role equally if not better, and is practically given to you at the Lake of Rage. The main selling point is that this makes the Elite Four so much easier.
Fire starts off rather well, being neutral in the first, good in the second, neutral up until Jasmine and Pryce where Steel and Ice are melted down by Fire, and then resuming neutrality against the final gym.
It wasn't until 3rd and 4th gen that I saw that Fire types prevailed. Having access to flying moves early on in Gen 3, made many gyms easy such as the fighting gym. I don't remember much from Gen 3. It is the worst generation out of the 4...Infernape is without a doubt a powerhouse in Gen 4. Having Close Combat and Flamethrower made many gyms fall without much effort. If it wasn't weak to Fire, then it was weak to Fighting and against annoying Bronzongs, the converse was conveniently true.
Oh, and whoever said that Skarmory is not a physical tank, you sir, fail. That is EXACTLY what Skarmory is and one of the best I might add.
Whoever said that Blastoise is good with Earthquake and other physical attacks, well that answers your question as to why it's not very good offensively. It would do much better with Surf and Ice Beam.
You cannot generalize so much by saying all of one type is this and all of another is this. Take Venusaur for example. It is a capable physical sweeper, where Meganium is generally a support type. Look at Blastoise, mainly used as a bulky spinner or crappy staller without a recovery move and sometimes a special sweeper (in first gen you really have no choice but to make it a sweeper), where Feraligatr has monstrous attack and a vast sweeping potential.
And yes, there is speed in 4th gen. Look at Infernape. It rivals the speed of Starmie. Come on, do some research before posting.