It really depends on how you define this question.
How many different characters? Possibly hundreds.
How many series? There's quite a few; G1, Beast Wars, Beast Machines, Robots In Disguise, Armada, Energon, Animated, the live action movie... The toys follow this theme, but also have side series like Alternators and Classics.
How many movies? Currently two (but soon to be three), one being from the 80s involving the G1 storyline, and the live action series released in 2007. And now Transformers 2: Revenge of the Fallen said to be released June 26th, 2008.
If you really want to see all there is to know, do a Google search for a Transformers Wiki, they usually have tons of info to provide. Better yet, here's one; http://transformers.wikia.com/wiki/Main_Page
3 so far transformers, transformers revenge of the fallen and transformers dark of the moon
Many reviews of the Transformers 2 movie are only average of below average. Many consumers stated that it is poor continuation from the first Transformers movie.
not that many
None.
Two.
68
Que Ironhide Whellie Brains
3 so far transformers, transformers revenge of the fallen and transformers dark of the moon
Many reviews of the Transformers 2 movie are only average of below average. Many consumers stated that it is poor continuation from the first Transformers movie.
Transformers: Generation 2 has twelve issues in total .
4.5
Transformers 2 has been rated as a 3 star movie
not that many
None.
100
4
Two.