English speakers: which of them is right (grammatical doubt)?

Were is correct, in the context of "I wish I were..." (as were indicates a desirable state in this context, not something that has actually happened), but you will commonly here was as well. Was is appropriate for use with I when indicating an event that has already happened, such as I was at the party last night, or I was living in Houston before I moved here. Were is also appropriate for a past event that has happened, but when used with "we" For example, We were so tired last night.