Pokémon Red and Blue: Route 1 II

Now that you are equipped with Poké Balls, you can catch Pidgey and Rattata on this route.

Pidgey, Pidgeotto and Pidgeot - Acceptable
Pidgey is a sturdy Flying-type. It has an advantage against the third gym; however, it does not learn a Flying-type move until level 31. If you're playing with a full team of six, this can be very late. Likely well past the third gym; however, it becomes all the sturdier when it evolves into Pidgeotto at level 18 and again into Pidgeot at level 36.
As discussed on Route 22, it learns Sand-Attack very early at level 5. This makes the opponents moves much less likely to hit, which is such a handicap that similar moves have been banned from the competitive scene. It is also noteworthy that it gains STAB from Normal-type moves like Quick Attack, Take Down and Double-Edge. Like most Flying-types, it can also learn Fly, a two turn Flying-type move that can be had before the third gym.
It can be outclassed by other Flying-types, including Spearow, who learn a move called Drill Peck, which is the most powerful single-turn Flying-type attack in this generation. Sky Attack is a two turn move with 140 base power, giving it an effective power of 70 per turn, although on the first turn it is completely vulnerable. Fly is a two turn move with 70 base power, on the first turn it can only be hit by Swift; however, it has an effective power of only 35 per turn. Drill Peck is 80 power, every turn, no strings attached, and Pidgey does not get it.

To be fair, like most Normal-types, Hyper Beam can be devastating, and, in the first generation, it does not have to recharge if it defeats the opposing Pokémon. Pidgeot also gets the versatile Mirror Move (at the excessive level of 54, mind you) which reiterates the opponents last Water, Grass, Electric, Ice, Psychic or Dragon move.

Rattata and Raticate - Recommended
Rattata and Raticate have not aged well, but in these games, they are very well rounded Pokémon. The Normal-type was bested only by the all-powerful Psychic type in generation 1. Rattata is a strong attacker and becomes more so when it evolves into Raticate at the early level of 20. Also, at the one badge level of 14, Rattata learns a move called Hyper Fang. With 80 base power, Hyper Fang can sweep through the beginning of the game.
The other move that makes these Pokémon unique is Super Fang. Super Fang cuts the opponent's HP in half. This is powerful, because it disregards Attack and Defense entirely. This allows Raticate to devastate competitive staples like Starmie. Super Fang also almost guarantees getting double the value out of Hyper Beam by negating the recharge. Also, in a single player game, Raticate can get good use out of other essentials like Body Slam and Double-Edge.

After catching Pokémon, continue on to Viridian City again.

Proceed to Viridian City

Advance to Route 2