About 400, depending on where you cut off Gen1, and how many "extras" you include - like Mail-away, Mini-spies, Minibot variants and My First Transformers.
(list below is from my collection site)
1984 - 28 + 3 Extras
Decepticons - Megatron, Soundwave, Buzzsaw, Skywarp, Starscream, Thundercracker, Frenzy, Laserbeak, Ravage, Rumble.
Autobots - Optimus Prime, Bluestreak, Hound, Ironhide, Jazz, Mirage, Prowl, Ratchet, Sideswipe, Sunstreaker, Trailbreaker, Wheeljack, Brawn, Bumblebee (yellow), Cliffjumper (red), Gears, Huffer, Windcharger.
Extras - Bumblebee (red), Bumblejumper, Cliffjumper (yellow).
1985 - 50 + 12 Extras*
Decepticons - Shockwave, Dirge, Ramjet, Thrust, Astrotrain, Blitzwing, Barrage, Chop Shop, Ransack, Venom, Bombshell, Kickback, Shrapnel, Bonecrusher, Hook, Mixmaster, Long Haul, Scavenger, Scrapper.
Autobots - Omega Supreme, Jetfire, Blaster, Roadbuster, Whirl, Perceptor, Slag, Sludge, Snarl, Swoop, Grimlock, Grapple, Hoist, Inferno, Red Alert, Skids, Smokescreen, Tracks, Topspin, Twin Twist, Beachcomber, Cosmos, Powerglide, Seaspray Warpath.
Mail Order - Sky Dasher, F-1 Dasher, Drill Dasher, Camshaft, Downshift, Overdrive.
Extras* - (Mini-Spies) Mazda/FX-1 (white), Mazda/FX-1 (yellow), Mazda/FX-1 (blue), Jeep (white), Jeep (yellow), Jeep (blue), Dunebuggy (white), Dunebuggy (yellow), Dunebuggy (blue), Porsche (white), Porsche (yellow), Porsche (blue).
1986 - 58 + 3 Extras
Autobots - Broadside, Sandstorm, Springer, Hotspot, Silverbolt, Air Raid, Firefight, Skydive, Slingshot, Blades, First Aid, Groove, Streetwise, Metroplex (with Scamper, Slammer, Sixgun), Sky Lynx, Ultra Magnus, Rodimus Prime, Blurr, Hot Rod, Kup, Wreck-Gar, Hubcap, Outback, Pipes, Swerve, Tailgate, Wheelie, Eject, Ramhorn, Rewind, Steeljaw.
Decepticons - Trypticon (with Fulltilt, Brunt), Galvatron, Cyclonus, Scourge, Octane, Gnaw, Runabout, Runamuck, Ratbat, Motormaster, Onslaught, Divebomb, Headstrong, Rampage, Tantrum, Razorclaw, Blast Off, Brawl, Swindle, Vortex, Breakdown, Dead End, Drag Strip, Wildrider.
Mail Order - Spectro, Spyglass, Viewfinder.
Extras - (My First Transformers) Car-Bot, Jet-Bot, Truck-Bot.
1987 - 51
Autobots - Fortress Maximus (with Cerebros, Spike, Cog), Brainstorm (with Arcana), Chromedome (with Stylor), Hardhead (with Duros), Highbrow (with Gort), Scattershot, Doublecross, Grotusque, Repugnus, Blurr (with Haywire), Crosshairs (with Pinpointer), Hot Rod (with Firebolt), Kup (with Recoil), Pointblank (with Peacemaker), Sureshot (with Spoilsport), Punch/Counterpunch, Cloudraker, Fastlane, Afterburner, Lightspeed, Nosecone, Strafe, Chase, Freeway, Goldbug, Rollbar, Searchlight, Wideload.
Decepticons - Scorponok (with Zarak, Fasttrack), Sixshot, Apeface (with Spasma), Snapdragon (with Krunk), Mindwipe (with Vorath), Skullcruncher (with Grax), Weirdwolf (with Monzo), Hun-Gurrr, Cyclonus (with Nightstick), Misfire (with Aimless), Scourge (with Fracas), Slugslinger (with Caliburst), Triggerhappy (with Blowpipe), Pounce, Wingspan, Battletrap, Flywheels, Blot, Cutthroat, Rippersnapper, Sinnertwin, Overkill, Slugfest.
1988 - 60
Autobots - Optimus Prime (with Hi-Q), Quickswitch, Getaway (with Rev), Joyride (with Hotwire), Slapdash (with Lube), Cloudburst, Groundbreaker, Landmine, Sky High, Splashdown, Waverider, Catilla, Chainclaw, Gunrunner, Hosehead (with Lug), Nightbeat (with Muzzle), Siren (with Quig), Landfill (with Silencer and Flintlock), Quickmix (with Ricochet and Boomer), Scoop (with Tracer and Holepunch), Fizzle, Guzzle, Sizzle, Backstreet, Dogfight, Override, Grandslam, Raindance.
Decepticons - Doubledealer, Darkwing (with Throttle), Dreadwind (with Hi-Test), Bomb-Burst, Bugly, Finback, Iguanus, Skullgrin, Submarauder, Carnivac, Snarler, Roadgrabber, Snaptrap, Nautilator, Overbite, Seawing, Skalor, Tentakil, Fangry (with Brisko), Horri-Bull (with Kreb), Squeezeplay (with Lokos), Needlenose (with Zigzag and Sunbeam), Quake (with Heater and Tiptop), Spinister (with Hairsplitter and Singe), Cindersaur, Flamefeather, Sparkstalker, Crankcase, Ruckus, Windsweeper, Beastbox, Squawktalk.
1989 - 57
Autobots - Skyhammer, Crossblades, Vroom, Doubleheader, Longtooth, Pincher, Bumblebee, Grimlock, Jazz, Roadblock, Countdown, Groundshaker, Hot House, Ironworks, Erector, Overload, Highjump, Mudslinger, Powertrain, Tote, Free Wheeler, Roadhandler, Swindler, Tailspin, Big Shot, Flak, Sidetrack, Sunrunner, Fixit, Red Hot, Seawatch, Stakeout.
Decepticons - Thunderwing, Bludgeon, Octopunch, Stranglehold, Starscream, Birdbrain, Bristleback, Icepick, Scowl, Slog, Wildfly, Skystalker, Skyhopper, Airwave, Greasepit, Flattop, Roughstuff, Nightflight, Storm Cloud, Tailwind, Whisper, Blackjack, Detour, Hyperdrive, Road Hugger.
1990 - 85
Autobot Actionmasters - Blaster, Bumblebee, Grimlock, Inferno, Jackpot (with Sights), Jazz, Kick-Off, Mainframe (with Push-Button), Rad (with Lionizer), Rollout (with Glitch), Skyfall (with Top-Heavy), Snarl (with Tyrannitron), Over-Run, Prowl, Optimus Prime, Sprocket, Wheeljack.
Autobot Micromasters - Full-Barrel, Overflow, Retro, Surge, Pipeline, Gusher, Blaze Master, Eagle Eye, Sky High, Tread Bolt, Crumble, Groundpounder, Neutro, Takedown, Big Daddy, Greaser, Hubs, Trip-Up, Big Hauler, Heavy Tread, Hydraulic, Slow Poke, Barrage, Heave, Moonrock, Missile Master, Phaser, Blast Master, Oiler, Slide, Strikedown, Power Run, Wheel Blaze, Road Burner.
Decepticon Actionmasters - Banzai-Tron (with Razor-Sharp), Devastator (with Scorpulator), Krok (with Gatoraider), Shockwave (with Fistfight), Soundwave (with Wingthing), Treadshot (with Catgut), Axer, Starscream, Gutcruncher, Megatron.
Decepticon Micromasters - Blackout, Spaceshot, Terror-Tread, Cement-Head, Bombshock, Dropshot, Growl, Tracer, Barricade, Ground Hog, Motorhead, Roller Force, Direct-Hit, Power Punch, Fireshot, Vanquish, Meltdown, Half-Track, Grit, Knockout, Sledge, Hammer, Stonecruncher, Excavator.
TOTAL - 389 + 18 Extras*
* plus another 12 if you count Mini-spies by allegiance, as each of the 12 colour/mould varieties had an Autobot or Decepticon sticker.
Add about another hundred if you then want to include Hasbro figures released in UK and South America.