Oh dear I counted my ponies... ^^;
Individual category counts in the spoiler.
Spoiler
G1:
Original normal ponies: 84
Rerelease ponies: 9
Other ponies: 7 (1 petite, 1 ornament, 1 Running Press, 2 Loyal Subjects,
1 My Pretty Pony, 1 plush)
G1 Total: 100
G2:
Normal ponies: 11
Other ponies: 4 (2 McDonald's, 1 plush, 1 Friendship Gardens Sundance)
G2 Total: 15
G3:
Normal ponies: 112
Normal McDonald's ponies: 16
Plush: 6
So Soft baby ponies: 5
Ponyville ponies: 5
McDonald's Ponyville ponies: 3
Other ponies: 19
G3 Total: 166
G3.5:
Normal ponies: 14
Newborn Cuties ponies: 5
McDonald's ponies: 6
So Soft baby ponies: 7
Other ponies: 2
G3.5 Total: 34
G4:
Normal ponies: 96
Larger brushable ponies (by Hasbro): 16
Blindbag ponies: 40
McDonald's ponies: 27
Plush: 19 (one is handmade, not official)
So Soft baby ponies: 5
Other ponies: 43
Equestria Girls: 7
Equestria Girls Minis: 3
G4 Total: 256
G4.5:
Normal ponies: 47
Guardians of Harmony: 6
Plush: 8
McDonald's ponies: 5
Other ponies: 24
Equestria Girls: 7
G4.5 Total: 97
More basic count:
G1s: 100 (Normal ponies: 84, 93 if you include 25th and 35th anniversary ponies)
G2s: 15 (Normal ponies: 11)
G3s: 166 (Normal ponies: 112)
G3.5s: 34 (Normal ponies: 14, 19 if you include Newborn Cuties)
G4s: 256 (Normal ponies: 96, I included Spike)
G4.5: 97 (Normal ponies: 47)
"Normal ponies" means regular scale ponies, not styling size. I counted those as "larger brushable ponies" for G4 and "other ponies" in the other generations.
Normal pony count is 378 (including anniversary G1s and Newborn Cuties G3.5s). I have the most G3s in terms of normal ponies, the most G4s overall. I have the least of G2 in both normal ponies and overall ponies (curse these ponies being so rare in the wild!).
Total count is 668, this includes each figure and plush in my collection, sans G4/G4.5 pets. Last I had counted less than a year ago I was just over 500, not sure what happened, I guess a huge increase in the amount that I've been thrifting. Getting a job certainly helped.
I could have miscounted at any point during this, since I counted most of them manually (I really should work on adding more stuff to my Snupps, it'd help a lot), so 668 is the estimate but it could be a bit higher or lower.