Long term storage

[flyingdutchman]

Hi!

I have access to a pretty neat basement (doesn't even have that typical basement smell!) that I'm not using at all right now, but I was thinking about turning it into a little cellar. It's pretty dark, no windows and a constant temperature all year round.
I have been exploring wines now for a few years and I'm interested in maybe storing some wine long term... but have no idea which wines would actually improve over a few years time (knowing 90% of wines are to be consumed within 2 years after harvest).

So, my question is, what are the basic requirements for a wine to be suitable for storage for a few years? Type of grape? Region? Both? Sugar levels? I've read a little about it on other sites, they recommend some red Bordeaux (only crus classés) for example, but not the basic knowledge on which types of wines have the best chance of improving over the years...

Thru work (I'm in logistics of wines & spirits) I can get great deals if I buy larger amounts, so plenty of opportunities to fill up that cellar at a good price! Also, reading this website regularly, I noticed some people talk about "certificates of storage" - to prove the bottle has been stored properly. Just out of curiosity, because I will keep my wines for personal use only, but who issues these certificates and how can they check something like that?

Thanks!