Suicide can most definitely be cowardly. It is a way to escape problems at the expense of ones life. Finances, broken hearts, etc... these are *really* stupid reasons to kill oneself. They can be fixed. They are temporary. So yes, in these cases it is cowardly to kill oneself, as it deprives every single person who knew them of the chance to help them. It is cowardly because the person who is now dead does not have to deal with the consequences of their actions. If they die over finances, they pass that debt to someone else. If they do it over a broken heart, they broke countless more.
Depression and addiction are a bit different. In these cases I would generally not use the term cowardly, but that doesn't mean it isn't selfish. Even a depressed person or someone dealing with withdrawal is aware of the people it will affect. At some point they actively made the choice that death was a better option than life, despite how it will affect those around them.
I lost a good friend about 4 months ago. He had a 12 year old daughter and an 8 year old son. He loved them to death. He had a good job, a great house, a great wife. And then found himself drinking too much. He went to rehab for 3 months. 2 days after getting home he killed himself. Despite how much respect I had for him, it doesn't change the fact it angered me he would do that to his kids. He owed it to them to get through his issues. He owed it to his family as part of the contract you sign yourself up for when you choose to marry and have children. So yes, it was selfish for him to do that. Those kids grow up without a father now, because he was too focused on HIM HIM HIM. That is the very definition of selfish.
Now, sure, you can get into a world of what-ifs about this guy. Maybe he was terminal. Maybe he was mentally unstable. Maybe this, maybe that. It doesn't change the fact he chose to kill himself in a public place that is specifically geared towards families. That, without a doubt, is selfish. He either went in to that hotel knowing he planned to kill himself, or he got some crazy news while he was there that pushed him off the deep end.
If he went in knowing he was going to do it, then screw him. That is all about attention and selfish bullcrap.
If he decided to kill himself based on something that occurred while he was there, then I lean towards the coward side of things. I don't care what scenarios you hypothetically toss out there, you can not find one that I will say, "Oh ya, hurling himself off the contemporary in front of families was a justified reaction."