Like, it would be great the possibility to transfer games to Steam.

You cannot transfer games from GOG to Steam, sorry.

No can do my dude

Well, you still get to keep all the installers you downloaded and you are free to back them up anywhere. You will also be able to install and play the games without a GOG account. (without Galaxy). But as the others said, you're not going to be able to transfer them to Steam. Steam is a competitor of GOG. So they are not going to give you free stuff just because you bought something here.

Steam transfer is a no.
However, since the installers and games are DRM-Free you can download them and contact Support in order to close the account if that's what you desire. Not that I can see any point in doing that...

You can always install the GOG versions and add them to your Steam library. You won't have them in your Steam account, obviously, but you can start them through Steam, if that's what you want.

About the only thing you could do is to contact the publisher of each game you have on GOG, and ask them if they will give you a free Steam key for each game. Maybe with a proof of purchase, like the receipt of each game you got into your email when you bought and activated the games on GOG.

Some might even give you a free key, while others not.

After that you can ask GOG support to delete your account, or I don't know why you even want to do that, you can simply stop using your GOG account, right? Why do you need to specifically delete it?

Why not ask publishers to give you a GOG key for all your steam games, then move here and delete your steam account?

2 out of 10 of effort for trolling. This is weak sauce - why would you ever move your games to Steam?

So you came from Steam to GOG and now back to Steam? Tell us your secret sauce of life. Cheers

I guess they were confused by the whole DRM-Free thing. The fact of actually owning (rather than renting) your games in this day-and-age can be rather scary thought for some...

Seems like it. Especially when they accidentally download the offline installers, and God forbid the games launch without a client. Pure horror in this day and age.

Regarding your original question:
If you delete your account, you will loose the ability to download the installer files and any further updates/patches for any games you have purchased. However, the installation files for any games you purchased prior to deleting your GOG account will continue to work. So: at the moment your account is terminated, you'll still have access to whatever you previously downloaded; but you'll never be able to download anything more.

In regards to transferring a GOG purchase to Steam: Steam has never allowed a GOG purchase to transfer to their service, and they have very little reason to do so in the future. GOG has occasionally been able to work deals with game publishers to allow a Steam purchase to transfer into GOG, in the hopes that doing so will compel gamers to purchase more games on GOG. But Steam -- being the juggernaut that they are -- has almost zero incentive to do a similar arrangement for GOG purchases. GOG wants to incentivize you to purchase on their platform, whereas Steam wants to penalize you for not purchasing on their platform.

Back to your original question: there is almost no legitimate reason to delete your account. Don't post on the forums, and don't purchase any further games if you're really ticked off with GOG. But deleting your account will only deprive you of the products and services that you have legitimately purchased.

Heck, if you're really pissed off with GOG and want to "stick it to da' man!" then keep your account active and only download the free games they periodically release.

If the games were downloaded or purchased with a specific account then yes, you will lose all of them by deleting the account.

Why?

but to answer your question, yes.
you own the License for the games, opposed to Steam where you have a subscription to content that revokes associated licenses.

You can download offline installers, opposed to steam which will only download via the client

If you used the galaxy client to download, you can delete that and your games will still work, opposed to steam where the games won't.

So again i ask Why do you want to move to an arguably inferior system?