Canadia in my opinion is the best card in the game. CC is really great, but Canadia has far more utility. It can block an attack, you can get a free monster, it's flexible, and the advantage of flipping a monster facedown is extremely valuable. As a player who has both, I use Canadia far more than CC.
Nope. There's still play to be seen with only 1 single canadia; but 1 sarcophagus? Nah.. it is useless without at least 2 copies in your deck (think greener grass). Plus canadia is 100 times more useful than sarcophagus. If there's only 1 empty slot in your deck would you choose cana or sarco??
I get your point but for OP (a free2p player) you think exclusives is more important or practical is of higher priority? Heck even choosing CC or sphere (if he decides to open canadia box) is better choice than sarco.
What's worth getting mostly comes down to the player. I spent my first one on Buster Blader, the Dragon Destroyer Swordsman. Still haven't spent my second since there's nothing I absolutely need right now and I have like a year to decide.
I prefer Floodgates but yes Canadia is excellent because it allows you to do two things - cut something off instantly at a critical stage (eg equipping), buying you a turn in the process and also summon a creature from the graveyard to tribute on or do whatever else these crazy kids do with creatures nowadays.