I'm down to my last choices on a car

2015 mazda 3 5-door; trim; s touring
2015 subaru wrx; trim; premium (automatic)
2015 mazda 6; trim; touring
2015 honda accord; trim; (sport or ex)
2015 nissan altima; trim; 2.5sv

which would you choose && why?

also if any other suggestions on a dependable car under max budget of 30k would be helpful

2015 Honda Accord EX. Best reliability, lowest cost of ownership, and best resale value. The EX is more comfortable than the Sport and will also be slightly less on cost of ownership for the time you own it. Also, consider the all new redesigned 2015 Toyota Camry XLE.

What is their not to like with the 6? I would argue lowest cost of ownership, do you plan to sale it or pay it off? Check reliability in the last five years, Honda is not the Honda of old. Mazda is right up there. Subaru is a good choice but the design language is not hitting on much. Reliable well built and lasts a life time. Mazda's 3 is a compact, it can be tight for driver and a passenger. Its doable but not much room to spare like its mid-sized counterpart. The 2.0 liter engine gets better gas mileage than the 6 I do believe. Its rated at 40 mpg. Nothing wrong with Nissan, personally I never liked one enough to buy it. I would drive both Mazdas and Subaru.actually all you are considering they will separate from the pack.

I just bought a 2014 Accord LX 4 cylinder because it provides the best combined fuel economy, reliability, resale value and comfort.
The 2015 is basically the same car and that would be my recommendation if these 4 things are equally valuable to you.

The Mazda 3 would be an equally good choice, but I did not find it as comfortable.
The Mazda 6 is great but it's just too expensive.
The WRX is not as comfortable and the fuel economy is not there. In exchange you get AWD and more power, if those things are more important to you.
The Nissan CVT sucks.