Okay, here goes...
IMPORTANT: Thousands of better photographers than myself will have a different opinion, and this is just my own. My critiques of your pics obviously makes my efforts open to other opinions, which are very welcome. I certainly do not expect everybody to agree with my so-called improvements, and some might even say that they are downright kak.
PIC ONE:My opinion:
1. The image is too cluttered and lacks a definite subject.
2. The notice board in the background distracts my attention from what I am supposed to be looking at.
3. The placement of the keys exactly in the middle of the frame does not work.

My attempt:
I will focus on something specific in the scene.
The keys make for an interesting subject, and placing them on thirds will make for better composition.
PIC TWO:My opinion:
1. Personally I have a problem with horizons which are not level. Not everybody will agree on this point but, in my opinion, unless you are going for a specific effect the horizon should be level.
2. It seems like it wasn’t a good time of the day for a landscape shot like this, because the light is a bit flat and the pic lacks colour and contrast. The same shot very early in the morning or late afternoon would probably have been great.

My attempt:
Levelled the horizon.
I tried to add some color and contrast to the posted pic (would have been easier if it were the original file).
I tried a more panoramic crop.
PIC THREE and FOUR:My opinion:
1. There is not enough sharpness, detail or colour in the birds for these to qualify as bird photos, and serious bird photographers will probably have a lot of bad things to say from that perspective.
2. Then, as landscape shots, the black blobs (birds) add nothing to the pics.

PIC FIVE:My opinion:
1. Lekker photo, with great colour and simple, effective composition.
PIC SIX:My opinion:
1. Great idea for a pic, but unfortunately the light is also very flat in this one.
2. More detail in the rock in the foreground would have been nice. I would have made use of ActiveD Lighting on “high” setting on the Nikon here.
3. It seems that the pic lacks depth of field. A smaller aperture would have fixed this.
4. Placing both the rock and the lighthouse on thirds would have improved the composition.

My attempts:
More panoramic crop, and converted to grayscale and added lots of contrast to try to fix the light to make the sky more dramatic.

More panoramic crop, and added saturation and contrast.

Tried a different crop altogether.
PIC SEVEN:My opnion:
1. This pic lacks a subject. Period.

Okay, that’s it for now. I am sure you will understand that this is just an attempt to share what I have learnt from others, and is by no means a professional opinion.
Additional note: The best advice for landscape shots such as these is usually to take the shots at the right time of day. Apparently the serious landscape photographers do not even touch their cameras after 09:00 or before 16:00, because during the day our African sunlight is just too harsh for taking good pics.