Here is my take on every PS4 game that I've played so far (which isn't that many)
1. NBA 2K14 - This is my killer app. Period. This game justifies getting a next-gen system imo. (there are some possible microtransaction concerns in this game, but I haven't bumped into them yet)
2. Resogun - Easily the best PS4 exclusive at the moment.
3. Madden 25 - Eh, I'm not sure I would recommend this to anybody but hardcore football fans. It's decent, but overall, pretty underwhelming. I only got it because I haven't played a Madden in years.
4. Fifa 14 - I've only played the demo, but it seems to play well, but doesn't look very next-gen at all (imo). You need to play this on a super HUGE tv to really notice anything next-gen about it.
5. Trine 2 - Only tried the demo but liked what I played. I think this game should be 10 bucks though. You can get this game for like 3 bucks on the PC. I tried the 3D mode, and it was pretty cool. If this was $10, I'd probably buy it.
6. Killzone :SF - Yeah, this is a big disappointment for me. The checkpointing in the game is absolutely horrible, and it's very hard to know where the heck you're supposed to go, and what exactly you're supposed to do. The alarm thing is really dumb imo. Just makes the game very irritating. Also, this game does seem a bit rough around the edges in certain ways. When your guy dies, it seems like it's a game from 1999 or something. Like the way the camera tweaks out when your guy dies. Graphics can be very nice in certain areas, but it's hard to really enjoy it with the clunky gameplay.
7. Contrast - Only played this game one time, and I don't think I'm ever going to play it again. Seemed really rough and unpolished. Seems almost unfinished to me.
8. Marvel Lego - Only played the demo, but wasn't impressed at all.
PS4 Games I'd most like to try that I've never played:
1. Knack - might as well try the other 1st party game at some point. Waiting to see it for like $29.99 or something.
2. Assassin's Creed 4 - Heard that the PS4 version is very Purdy. Would like to check it out, just to see how it looks.
3. Need for Speed Rivals - I've heard some nice things about this game. I'm currently playing Forza 5, so don't need a racing game right away, but wouldn't mind trying it out.
4. Flower - I might buy this game. I played it a bit on PS3 and it was pretty cool. Heard the PS4 version looks great. I think it's a really short game though. so maybe wait for it to be even cheaper for PS+ members or something. I know it's the cheapest game on PS4 already, but I'm talking like a $3.99 special, lol.
5. Battlefield 4 - If they ever get this game fixed where it's in a decent, playable state, I'd like to try it.