I'm currently at level 11, here's a list of the pokemon I've seen from most to least
Pidgey: 35
Weedle: 28
Eevee: 21
Rattata: 21
Drowzee: 16
Caterpie: 13
Spearow: 12
Venonat: 11
Cloyster: 9
Oddish: 7
Kakuna: 6
Pidgeotto: 5
Paras: 5
Zubat: 4
Poliwag: 4
Squirtle: 3
Metapod: 3
Bellsprout: 3
Nidoran (M): 3
Jigglypuff: 3
Psyduck: 3
Magikarp: 3
Gastly: 2
Pidgeot: 2 (1 Evolved and the other was an encounter, I wasted like 40 poke balls, not from it breaking out, only about 5 actually hit the bird. Most of them just kind of fell out of my hand onto the ground. I eventually just ran it was so bad.)
Nidoran (F): 2
Krabby: 2
Koffing: 2
Horsea: 2
Goldeen: 2
Staryu: 2 (One fled and the second hatched from an egg today)
Scyther: 2
Jynx: 1
Tauros: 1
Slowpoke: 1
Seel: 1
Fearow: 1
Venomoth: 1
Meowth: 1
Mankey: 1
Haunter: 1
Hypno: 1
Vaporeon: 1 (Evolved)
Jolteon: 1 (Evolved)
Gloom: 1 (Evolved)
Raticate: 1 (Evolved)
Beedrill: 1 (Evolved)
I'm kind of surprised the Nidoran and the Magikarp's are so rare. I heard you get great balls at level 12, maybe Rattata and Venonat stop spawning at level 12 as well, would love to see a Bulbasaur or a Sandshrew.
I find over 9000 Pidgey and Rattata in Blaine, MN.
In my area, Poliwag, Pidgey, and Rattata.