Simple. There is no other game like Tibia. The graphics make this game for me, its the one thing that makes the game more nostalgic.
It's hectic, but peaceful. It's scary, but satisfying. Tibia punishes you if you die, and rightly so, it makes hunts that bit more exciting, when you drop to low health and your heart beat increases! You sweat! You panic! YOU HIT THE HEALH POTION KEY AND PRAY!
It's endless, really, its entirely up to you on what you do, where you go, who you intergrate with and what you hunt!
You can pick from 4 vocations, be a druid, knight, paladin or sorcerer. Wield mighty swords, axes or clubs to swing at foes, throw enchanted spears with pinpoint accuracy for incredible damage...or perhaps throw magic around like the very next Gandalf.
The. Choice. is. YOURS.
For me, Tibia could improve greatly with two things:
1) its initial starter game and explain a little more until level 30 or so. Getting someone to start is one thing, getting them to stay is another.
Just small hints such as:
"Great! You just reached level 14! Rumour has it that certain NPC's will offer you a spell to increase your speed temporarily, it could save your life, or just make those longer trips a little less bleak"
"Wow, level 20! Legend talks of an underground ritual in the dessert you may be interested with, perhaps there is a reward? Maybe a sacrifice? Speak to fellow veterans to hear their opinions on this dessert mystery!"
2) Have a more expansive outreach to attract more players, sure they tried greenlight on Steam, but i'd like to see more from them. If anything their attempts to attract players is lacking, it relies heavily on the "introduce a friend" or the "return to tibia" schemes. They need to advertise more themselves, spend some of that 11 million euro income from 17-18.
The majority of players now are old school, getting someone to start tibia can be tough, but if they can stick it out ~6 months, i can guarantee you - their hooked.