I've gotten over 300 hours of enjoyment on Terraria.
I do enjoy games like Cargo Bridge, though, but definitely not for as long.

EDIT: Another thing is that 1. Terraria just updated to 1.3. Unlike Minecraft updates, the ones in Terraria (1.1, 1.2, 1.3) add a LOT of things. I've gone back and played 1.3 and it feels new and fresh. Of course, I'm a fan of those games.
2. Terraria sometimes goes on sale for only 3 bucks. That'd definitely something to watch for.

TacoMaster211
I think its like an MMO because of all of the bosses. Not a fan of those...

The bosses are a pretty integral part of Terraria. If you don't like them, I wouldn't suggest buying it. While they aren't all required (except for Wall of Flesh if you want to go into Hard Mode), they do unlock a lot of the game and are the only way to get certain items.

Terraria
Hands down terraria

Namez

TacoMaster211
I think its like an MMO because of all of the bosses. Not a fan of those...

You aren't forced to fight the bosses.

Well not exactly, but fighting the bosses is the only way to progress throught the game to obtain better gear. and some bosses spawn randomly on their own once certain requirements are met. o3o

TacoMaster211

AzieTerraria is fantastic. It's super content-rich for the price, is really pretty, and you can build some neat characters and bases with it. Haven't heard of the other game personally, but if you don't have Terraria, I think it's a great addition to anyone's library.

TacoMaster211
Terraria:

Pros:
Like Minecraft
Fun
Great Mechanics
Not very laggy

Cons:
More like an MMO type game (not a fan of those)
Complicated
Confusing
Hard

Not sure how this is like an MMO? It can be played in single player or multiplayer comfortably and you can progress through the content in any order you want to provided you have the skill and knowlege to survive. Not sure how the game is confusing either. Perhaps the sheer amount of items and their combinations could be overwhelming though.

I think its like an MMO because of all of the bosses. Not a fan of those...

You aren't forced to fight the bosses.

AzieTerraria is fantastic. It's super content-rich for the price, is really pretty, and you can build some neat characters and bases with it. Haven't heard of the other game personally, but if you don't have Terraria, I think it's a great addition to anyone's library.

TacoMaster211
Terraria:

Pros:
Like Minecraft
Fun
Great Mechanics
Not very laggy

Cons:
More like an MMO type game (not a fan of those)
Complicated
Confusing
Hard

Not sure how this is like an MMO? It can be played in single player or multiplayer comfortably and you can progress through the content in any order you want to provided you have the skill and knowlege to survive. Not sure how the game is confusing either. Perhaps the sheer amount of items and their combinations could be overwhelming though.

I think its like an MMO because of all of the bosses. Not a fan of those...

Exactly what Azie said haha. ^^ I love Terraria, it's amazing. Though as Azie said the content could be confusing at times. >u< I've played 350+ hrs on Terraria and I I've been playing it with a friend and it's so fun. ;w; I haven't heard of Poly Bridge, so I can't speak for it. (Pros and cons) However, it's up to you. Though I totally recommend Terraria if you were to buy it. c:

Terraria is fantastic. It's super content-rich for the price, is really pretty, and you can build some neat characters and bases with it. Haven't heard of the other game personally, but if you don't have Terraria, I think it's a great addition to anyone's library.

TacoMaster211
Terraria:

Pros:
Like Minecraft
Fun
Great Mechanics
Not very laggy

Cons:
More like an MMO type game (not a fan of those)
Complicated
Confusing
Hard

Not sure how this is like an MMO? It can be played in single player or multiplayer comfortably and you can progress through the content in any order you want to provided you have the skill and knowlege to survive. Not sure how the game is confusing either. Perhaps the sheer amount of items and their combinations could be overwhelming though.

I much prefer Terraria , you will get a lot more hours of gameplay out of it.

Poly bridge gets boring quickly.

I'm still not bored with terraria and I have 102 hours ingame.

I have only played Terraria, and to me, Terraria gets boring after you have beaten /achieved/gotten everything, since it is a path oriented game (story but it doesnt really have one, just bosses). However I do not know about Poly Bridge, but I hope i helped your decision.

However I do think Terraria is very fun for the times when you haven't beaten it

I own Terraria, both on Xbox 360 (Which I beat every boss in the game) and the PC (Which I just hack using CheatEngine). Since there's the ability to share characters apon different worlds, you could reach endgame on one and replay Terraria on the other, with all the best gear. Great concept, greater gameplay.
I can't speak for Poly Bridge, however I reasearched the game and It looks kinda like a free bridge builder game thats on Hoodamath.com. But, It is your money. Spend it how you see fit..