Let's start with the long one, to Hurstbridge. I suppose it is our longest suburban train trip at about 1 hour and ten minutes. Hurstbridge doesn't really feel like a suburb, more like a country town. You will pass by all the sporting complexes Melbourne is well known for, including the Melbourne Cricket Ground then you are elevated above the cheek by jowl housing and commercial sites of Richmond and Abbotsford then slowly the blocks of the land will become larger and the housing more grand as you head into the middle class eastern suburbs and then the 'mud brick house' area around the very conservation minded Eltham.
The gap between stations starts to increase and there is some single railway line, so at times there are pauses while waiting for a train to pass. The train reaches the countryside, with farms and some bushland. Hurstbridge itself has at least one very nice cafe near the station.
Oh yes, our train system is very modern. Photo from Heritage Council Victoria.
The other train trip I like is to the southern suburb of Sandringham, right on the beach. Beginning in the trendy inner suburbs south of the city, through the very expensive area of Brighton and the just expensive areas subsequently. Between Brighton Beach towards Hampton, the line travels along the seaside, so be sure to sit on the right hand side of the train. There is no shortage of cafes in Bay Road, Sandringham. You may want to break the journey by stopping off at what I suggest is Melbourne's nicest train station, Brighton Beach. There is a good cafe here too.
Right, here is an honourable mention for another train trip I enjoy, to Altona Village. While it is not very far, except in peak, a change of train is required. The change has worked well enough for me when I have taken the trip. I enjoy the trip across the paddocks and every time I have been, I have seen a rabbit in the grassland. The village in Altona is very peaceful and slow paced and a ten minute walk past the shops and cafes brings you to the very wide expanse of Altona Beach. The pier is not overly long and a nice stroll.