The example password "Tammy's#18bdayBIGpartyDroppedshibesweaterinpoolGMasonUsoon:(3yearsislong" on that page is weak.
Generating a NXT password is basically the same problem as creating a Bitcoin private key.
bitaddress.org is to my knowledge a fairly trusted site. You can take the private key it generates and use it as your password.
The human brain should not be used to generate a password because it is not a good source of randomness.
KeePass estimates 324 bit entropy for that passphrase. That's more bits than a NXT account with public key.
I'm not for trusting third party sites or software to do generation, though others may feel differently. I do welcome different views on the wiki

Feel free to register (PM joefox, the wiki admin) and edit, or comment in the talk page.
EDIT: Well, now that we've talked so much about that phrase, it's certainly become weak
