One form of peak experience can actually be communal.
Musicians and athletes speak of being "in the zone"--a state wherein the individual is no longer self-consciously aware of directing his actions. The musician is played by the music--the basketball player whips a pass to a spot before she knows a teammate will be there to recieve it. An individual performer may reach this state alone, but often the entire group is caught up together, as in some of the ecstatic performances of the bands of Miles Davis and Charles Mingus--or the Brazilian national team!
I've known people who were both musicians and athletes, and they attest that the experience of "the zone" is remarkably similar, no matter which activity it occurs in.
As a very amateur soccer player, I was, with my teammates, lucky enough to have experienced that transcendent state at least once. Everything started clicking at once--we moved perfectly into space, passes were one-touch and on, our game flowed seamlessly--it was as if our individuakity had merged, for those brief minutes, into a group mind.
The individual "zone" may be explained neuroscientificly by constant practice and repetition, but how can a group of individuals sublimate themselves into a sum greater than the parts?
In either case, a lot of dedication and hard work, along with some talent, is a prerequisite for that form of peak experience--it don't come easy.
I think it quite possible for communal religious experience can lead to "the zone"--For a Christian, praying alone is encouraged, but Christ pointed out that where two or three are gathered together in His name, He'd be sure to be there. Meditation for a Buddhist is a very personal experience, but the sangha, the community, I understand to be one of the bedrocks of the Buddha's teachings.
I certainly would not presume to rank either the individual or the collective peak experience as the greater.
I'm not from a tradition that particularly looked for communal transcendent experience, and I'd be interested in hearing from those for whom a church service can be a way for the community of believers to touch the divine together--