Formal:
* Abundant
* Ample
* Copious
* Extensive
* Plentiful
* Profuse
* Rich
* Numerous
* Myriad
Informal:
* A lot
* Lots
* Plenty
* Tons
* Heaps
* A bunch
* A ton
* A whole lot
Figurative:
* A feast (especially for the eyes or mind)
* A smorgasbord (especially for a variety of options)
* A cornucopia (especially for abundance and variety)
The best synonym to use will depend on the specific context and the desired tone.