I agree that it really depends on the person.  I have heard many people say that you either have an algebra mind or a geometry mind.  Meaning that one comes naturally and the other is a struggle.  That isn't always the case.  While I don't really like math, neither geometry nor algebra was particularly challenging for me.  Trigonometry is challenging simply because it requires a higher order level of thinking.  It is also advance mathematics.  Math builds on itself.  Any concepts that you haven't learned or don't understand will start to become more and more troublesome as you progress through mathematics. 

My experience was that Geometry involved a lot more logic and what to me was common sense. I found it easier because it seemed logical. Also how good you are at basic computation makes the biggest difference in all math classes. It doesn't matter how well you understand the idea or theory if you can't add subtract multiply and divide well, quickly and easily. However as a person whose computation is awful, that is also one of the reasons I found geometry easier.

Geometry is a little different from Algebra. I will say Algebra 1 can be used sometimes as a tool in geometry. 

To do well in geometry, you need to keep up with the theorems and definitions, and learn to show every step of your work.

Algebra 2/trig is a bit harder. But it is not that bad, as long as you keep up with your work DAILY. 

I found geometry easier than any of the other math courses in high school. I too was not very good at math, but geometry somehow clicked with me. Trig, not so much, and I struggled with calculus. I find myself now wishing I had taken math classes more seriously, since I actually find math to be pretty interesting. Suffice it to say I didn't see it that way when I was younger.

I have to agree with the above post. As an English major, I was never good at higher math, even in high school. I did manage to make it past Algebra I, Algebra II and geometry (barely), but luckily I didn't ever take trig. Don't know if I would have survived it.

If I were to rank them out in terms of difficulty it would be Algebra I, Geometry, Algebra II, then Trigonometry.  Again, that was my own experiences, and each person's own skill set will determine whether or not they excel or struggle with a particular subject.

Depends on what you're good at, right?  For me it wasn't.  For me, Geometry and Algebra I were pretty easy.  Then Alg II started getting hard and I was really bad at Trig.  It was partly the teachers, I think, but partly I just found that Geometry made more intuitive sense than Trig.