Yes, hellfire was made by sierra and like i said i liked it. Maybe cause most ppl didnt know that there was some hidden feature like a secret character and some other quests it was also possible to play multiplayer.

Here is a few game sierra has that are ok/good.
Half-Life
SWAT 3 Elite Edition
SWAT 3 Close Quarters Battle
Tribes 2
NASCAR Racing 2003 Season