The choice of electric guitar strings is huge, both in terms of brands and the sizes or gauge available. Gauges vary from really light 8s up to heavy 12s. Your choice of strings will depend on the type of music you play and what you feel comfortable with.
All guitarists will try a number of gauges until they find the ones they are most happy with. We always suggest that if you are unsure, start with 9 or 10 gauge strings and go from there.