BD-Rs are good, as well as the newer archival grade DVDs (Verbatim UltraLife, for example.)
My vote is to not just use a single medium. Every storage type has good and bad:
1: Cloud storage is easily accessible and easy to use... but is potentially insecure, and the provider can go down taking your data with it.
2: SSD is fast and usable, but when it dies, there is zero chance of data recovery, long term, once the electronics bail the gates.
3: Tape is archival grade with extremely long lifetimes, limited lifetime warranties on media (not data stored), is fast, and has a high capacity... but tape drives are extremely expensive. There is also the issue of a standard to put data on and off, although LTFS helps mitigate this.
4: Optical is widespread with plenty of drives... but doesn't have much capacity, and some disks wind up with bit rot.
5: Hard disks are quite popular, easy to use, fast... but most have just a year warranty, and tend to fail.
6: Printing to paper is possible... QR codes are one way. There is a utility called Paperback (formerly named Paperbak) which prints files out. However, I have had issues with the 1.0 version and scanning back documents, although 1.1 seems to be a lot better at getting back data. Of course, this doesn't store much data, but paper burns at a lot hotter temperature than most other physical media, so it would be useful for storing recovery keys and such.
I recommend using redundant backup media types, combined with different backup programs, perhaps different encryption mechanisms (TrueCrypt, PGP, GnuPG, etc.) This way, if one can't find a backup or encryption program (I doubt you might be able to find a copy of TC in 10-15 years, but something that decoded PGP is likely to be around), there are other ways.
Backup utilities are also something to watch out for. Every program has a different way of stashing data. You don't just need the utility, but you will also need the license key for it... and even then, I've encountered consumer level programs which will still fail and demand an upgraded version before they might consider restoring data.
tl;dr, diversify. At the minimum, use an external drive with encryption for bare metal backups, and then have documents synced with a cloud provider (encrypted of course)... and occasionally burn critical stuff to optical media.