[eternalban]

The Upanishads posit a reality of consciousness that upends the common ("worldly") conceptualization: dream state was held to be a higher and more fundamental experience of reality. In this sense, the "worldy" experience was actually "slumber" and the dream world more "real". In the Gita, Krishna declares that what common people experience as "day" and "awakened" is "night" and "sleep" for the yogin.

The Sufis symbolized the worldly existence and our apparent multiplicity as 'foam on the surface of an ocean' (c.f. Quantum cosmology and quantum foam), with the true reality being the eternal sea.

In both, "the Real" is the true Self, the "infinitesimal" that is "the Most High"; and the "outward world" the microcosom and the true macrocosom the inner reality of Man.

[pmoriarty]

There are Hindu myths that speak of the world being a dream of Brahma (or of Vishnu, depending on the myth), and of the world ending when the dreamer awakes.

Buddhism (how could I have neglected to mention it?) also has the illusory nature of the world (and of the self) as a central tenet -- though what that actually means varies with the strand of Buddhism you're talking about.

The world as illusion was even a belief of some Gnostics, who lived a couple of thousand years ago.

[eternalban]

To complete this list (and also follow up to your hoped-for "escape from the simulation" /g) the Qur'an explicitly says that "this life is an illusion and a pastime" and in the Sura of the Jinn, we are informed by these non-Human sentient beings that they have been trying for a very long time to escape but have always been frustrated in their attempts.

Regarding Buddhism, in the Lotus Sutra, the Buddha, to the apparent dismay of a few thousand attendees -- they get up and leave! -- informs that the Three Vehicles are merely devices to reach various levels of understanding, and that this world ("a burning old house") was an attraction that attracted his children but unfortunately they got caught up in the illusion and now need enticements (the Three Vehicles) to rescue them from the burning old house.