There are a total of 150 Pokemon you can collect during the game. Here they all are!
01. Bulbasaur-grass/poison type-evolves at level 16
02. Ivysaur-grass/poison type-evolves at level 32
03. Venusaur-grass/poison type-no evolution
04. Charmander-fire type-evolves at level 16
05. Charmelieon-fire type-evolves at level 36
06. Charizard-fire type-no evolution
07. Squirtle-water type-evolves at level 16
08. Wartortle-water type-evolves at level 36
09. Blastoise-water type-no evolution
10. Caterpie-bug type-evolves at level 7
11. Metapod-bug type-evolves at level 10
12. Butterfree-bug/flying type-no evolution
13. Weedle-bug/poison type-evolves at level 7
14. Kakuna-bug/poison type-evolves at level 10
15. Bedrill-bug/poison type-no evolution
16. Pidgey-normal/flying type-evolves at level 18
17. Pidgeotto-normal/flying type-evolves at level 36
18. Pidgeot-normal/flying type-no evolution
19. Rattata-normal type-evolves at level 20
20. Raticate-normal type-no evolution
21. Spearow-normal/flying type-evolves at level 20
22. Fearow-normal/flying type-no evolution
23. Ekans-poison type-evolves at level 22;/
24. Arbok-poison type-no evolution
25. Pikachu-electirc type-evolves with thunder stone
26. Raichu-electric type-no evolution
27. Sandshrew-ground type-evolves at level 22
28. Sandslash-ground type-no evolution
29. Nidoran/Fem-poison type-evolves at level 16
30. Nidorina-poison type-evolves with moon stone
31. Nidoqueen-poison/normal type-no evolution
32. Nidoran/Male-poison type-evolves at level 16
33. Nidorino-poison type-evolves with moon stone
34. Nidoking-poison/ground type-no evolution
35. Clefairy-normal type-evolves with moon stone
36. Clefable-normal type-no evolution
37. Vulpix-fire type-evolves with fire stone
38. Ninetales-fire type-no evolution
39. Jigglypuff-normal type-evolves with moon stone
40. Wigglytuff-normal type-no evolution
41. Zubat-poison/flying type-evolves at level 22
42. Golbat-poison/flying type-no evolution
43. Oddish-grass/poison type-evolves at level 21
44. Gloom-grass/poison type-evolves with leaf stone
45. Vileplume-grass/poison type-no evolution
46. Paras-bug/grass type-evolves at level 24
47. Parasect-bug/grass type-no evolution
48. Venonat-bug/poison type-evolves at level 31
49. Venomoth-bug poison type-no evolution
50. Diglett-ground type-evolves at level 26
51. Dugtrio-ground type-no evolution
52. Meowth-normal type-evolves at level 28
53. Persian-normal type-no evolution
54. Psyduck-water type-evolves at level 33
55. Golduck-water type-no evolution
56. Mankey-fighting type-evolves at level 28
57. Primeape-fighting type-no evolution
58. Growlithe-fire type-evolves with fire stone
59. Arcanine-fire type-no evolution
60. Poliwag-water type-evolves at level 25
61. Poliwhirl-water type-evolves with water stone
62. Poliwrath-water/fighting type-no evolution
63. Abra-psychic type-evolves at level 16
64. Kadabra-psychic type-evolves when traded through game link
65. Alakazam-psychic type-no evolution
66. Machop-fighting class-evolves at level 28
67. Machoke-fighting class-evolves when traded through game link
68. Machamp-fighting class-no evolution
69. Bellsprout-grass/poison type-evolves at level 21
70. Weepinbell-grass/poison type-evolves with leaf stone
71. Victreebel-grass/poison type-no evolution
72. Tentacool-water/poison type-evolves at level 30
73. Tentacruel-water/poison type-no evolution
74. Geodude-rock/ground type-evolves at level 25
75. Graveler-rock/ground type-evolves when traded through game link
76. Golem-rock/ground type-no evolution
77. Ponyta-fire type-evolves at level 40
78. Rapidash-fire type-no evolution
79. Slowpoke-water/psychic type-evolves at level 37
80. Slowbro-water/psychic type-no evolution
81. Magnemite-electric type-evolves at level 30
82. Magneton-electric type-no evolution
83. Farfetch'd-normal/flying type-no evolution
84. Doduo-normal/flying type-evolves at level 31
85. Dodrio-normal/flying type-no evolution
86. Seel-water type-evolves at level 34
87. Dewgong-water/ice type-no evolution
88. Grimer-poison type-evolves at level 38
89. Muk-poison type-no evolution
90. Shellder-water type-evolves with water stone
91. Cloyster-water/ice type-no evolution
92. Ghastly-ghost/poison type-evolves at level 25
93. Haunter-ghost/poison type-evolves when traded through game link
94. Gengar-ghost/poison type-no evolution
95. Onix -rock/ground type-no evolution
96. Drowzee-psychic type-evloves at level 26
97. Hypno-psychic type-no evolution
98. Krabby-water type-evolves at level 28
99. Kingler-water type-no evolution
100. Voltorb-electric type-evolves at level 30
101. Electrode-electric type-no evolution
102. Exeggcute-grass/psychic type-evolves with leaf stone
103. Exeggutor-grass/psychic type-no evolution
104. Cubone-ground type-evolves at level 28
105. Marowak-ground type-no evolution
106. Hitmonlee-fighting type-no evolution
107. Hitmonchan-fighting type-no evolution
108. Likitung-normal type-no evolution
109. Koffing-poison type-evolves at level 35
110. Wheezing-poison type-no evolution
111. Rhyhorn-ground/rock type-evolves at level 42
112. Rhydon-ground/rock type-no evolution
113. Chancey-normal type-no evolution
114. Tangela-grass type-no evolution
115. Kangaskhan-normal type-no evolution
116. Horsea-water type-evolves at level 32
117. Seadra-water type-no evolution
118. Goldeen-water type-evolves at level 33
119. Seaking-water type-no evolution
120. Staryu-water type-evolves with water stone
121. Starmie-water/psychic type-no evolution
122. Mr. Mime-psychic type-no evolution
123. Scyther-bug/flying type-no evolution
124. Jynx-ice/psychic type-no evolution
125. Electrabuzz-electric type-no evolution
126. Magmar-fire type-no evolution
127. Pinsir-bug type-no evolution
128. Tauros-normal type-no evolution
129. Magikarp-water type-evolves at level 20
130. Garados-water/flying type-no evolution
131. Lapras-water/ice type-no evolution
132. Ditto-normal type-no evolution
133. Eevee-normal type-evolves with leaf, fire, or water stone
134. Vaporeon-water type-no evolution
135. Volteon-electric type-no evolution
136. Flareon-fire type-no evolution
137. Porygon-normal type-no evolution
138. Omanyte-rock/water type-evolves at level 40
139. Omastar-rock/water type-no evolution
140. Kabuto-rock/water type-evolves at level 40
141. Kabutops-rock/water type-no evolution
142. Aerodactyl-rock/flying type-no evolution
143. Snorlax-normal type-no evolution
144. Articuno-ice/flying type-no evolution
145. Zapdos-electric/flying type- no evolution
146. Moltres-fire/flying type-no evolution
147. Dratini-dragon type-evolves at level 30
148. Dragonair-dragon type-evolves at level 55
149. Dragonite-dragon/flying type-no evolution
150. Mewtwo-psychic type-no evolution