TITLE: Most manifolds are hyperbolic?
QUESTION [28 upvotes]: I heard the claim as in the title for a long time, but can not find the precise reference for this claim, what's the reference with proof for this claim? Thanks for the help. 
To be more precise, is there a canonical topology structure on the space $\Omega$ of all compact $n$-dim smooth manifolds, such that for any compact smooth $n$-dim manifold $M^n$, any neighborhood $U$ of $M^n$ in $\Omega$, there is a $n$-dim smooth manifold $N^n\in U$ such that $N^n$ admits a Riemannian metric with curvature equal to $-1$. Everything in my mind is just Riemannian hyperbolic, no complex structure involved.

REPLY [10 votes]: Some answers here explain why in small dimensions being hyperbolic is generic. Maybe surprisingly, in some sense being hyperbolic is actually rare in higher dimensions (while in other senses it is generic, as Igor Belegradek explains in his answer).
In "Counting hyperbolic manifolds" Burger-Gelnader-Lubotzky-Mozes proved that for $d\geq 4$ there is a constant $c(d)$ such that for $V$ large enough, the number of $d$-dimensional hyperbolic manifolds of volume at most $V$ is bounded by $V^{c(d)V}$.
Note that by Mostow Rigidity, a given manifold carries at most one hyperbolic structure, and if it does, this manifold is completely determinded by its fundamental group. What BGLM do is actually counting possible fundamental groups.
On the contrary, in dimension 3 there exist infinitely many different (pairwise non-homeomorphic) compact hyperbolic manifolds of uniformly bounded volume (examples could be obtained by Dehn filling a knot complement).
By taking a product with a $(d-3)$-dimensional torus, one sees that also changing "hyperbolic" to "non-positively curved" (sectional curvature in $[-1,0]$) gives infinitely many compact manifolds of uniformly bounded volume.
Maybe I should (and maybe I shouldn't) note that one can generalize the above counting result to the realm  of all pinched negatively curved manifolds of dimension $\geq 5$. We do this in a forthcoming paper with Gelander and Sauer. For this one should relay on Farrel-Jones Theorem instead of Mostow Rigidity.

REPLY [4 votes]: Although this does not answer your question, there are partial answers in dimension 3.  
For example, if you construct an orientable 3-manifold via a random Heegaard splitting (constructing the gluing map as a product of Dehn twists, this is where the "random" part comes in) then most 3-manifolds are hyperbolic. 
https://arxiv.org/abs/0809.4881
On a contrary note, I think the answer to your question will depend heavily on how you consider your manifolds to be generated.  Some processes are biased towards things like hyperbolic manifolds.  Others have drastically different biases.   In that regard I don't think there is any one answer to your question.