Why do views make you happy? Why does having a nice view from your window make you happy? (As in people ask for a hotel room with a nice view).

Could this be replicated by simply having a large TV screen showing a view?

What views make people the happiest/saddest?
"Nice" window views do improve well-being, but with "nice" meaning "nature" mostly:


  The most consistent finding in the literature is that people prefer natural rather than built or
  urban views from windows. Windows with views of nature were found to enhance work and well-being
  in a number of ways including increasing job satisfaction, interest value of the job, perceptions of selfproductivity,
  perceptions of physical working conditions, life satisfaction, and decreasing intention to quit
  and the recovery time of surgical patients. However, the access to a view did not improve the
  performance of students or actual productivity of office workers. 


and later


  The preference of people for natural over built or urban views is one of the earliest and most consistent findings in the window literature [numerous citations].


From Kelly M. J. Farley and Jennifer A. Veitch (2001) "A Room With A View: A Review of The Effects of Windows on Work and Well-being".

And apparently art works of nature do have some effect as well, but I don't know the exact level of substitutability (beyond "real is better"):


  But perhaps the quickest and cheapest way to reap the benefits of biophilia – albeit not the most effective – is to install artworks showing natural scenes. Browning cites a 2008 study in which office workers were put in a room with closed curtains, with a garden view or with a flat-screen TV with the same dimensions and view as the window. After they received a stressor, the blood pressure and heart rate of those volunteers with the real view dropped the fastest and lowest, followed by those with the simulated view. “Both real nature and representations of nature suffice,” Browning explains, but “real is better.” 


From https://www.ioshmagazine.com/article/office-wellbeing-desk-view which unfortunaltely doesn't have a references list, so I couldn't locate that study right away.



As for why people like nature better, an evolutionary theory (quoting again from Farley and Veitch) is that 


  In summary, Ulrich’s (1983) psychoevolutionary theory suggests that acquiring a capacity for
  restorative responding to certain unthreatening natural contents and configurations had important
  advantages for humans during evolution. These included rapid attenuation of stress responses following
  threatening encounters, and fostering recharge of physical energy. In fact, Ulrich (1983), argued that
  modern humans are biologically prepared to quickly and readily acquire restorative responses with
  respect to unthreatening natural settings, but have no such preparedness for most urban or built contents
  and configurations.


It was criticized by others though (for incompleteness etc.), and as with many such evolutionary explanations of psychological phenomena, it's hard to test. And the critics propose instead:


  In contrast to Ulrich (1983) and Ulrich et al., (1991), R. Kaplan and S. Kaplan (1989) proposed
  the Attention Restoration Theory (ART) arguing that recovery from directed attention fatigue (restoration
  of effectiveness) could be accomplished by using modes of attending that required no effort. For these
  authors, James’ (1892) concept of involuntary attention partially explained the preference of many people
  for natural rather than urban views. Natural environments, they argued, are restorative because the
  involuntary attention (or fascination) they engender requires no effort on the part of the perceiver. In this way, natural scenes are advantageous to human health because they provide an opportunity for recovery
  from mental fatigue. 


In fact ART proposes four factors that affect the restorative properties of a view:


  Fascination, as the ability of an environment to generate awe in people; the amount of awe can give the directed attention a rest as it appears the involuntary attention in its place. Being away, a feeling that can be in objective or subjective form, as a person can be far away from a location or let his or her mind let go from everyday life and worries. Extension [aka extent], referring to the connection between each element found in an environment; the feeling of being able to travel through the environment in order to look for information it provides to the observer. Compatibility, characteristics found in an environment that meet the preferences and goals of a person.


There is some empirical evidence that the Kaplans may be mostly correct, except for "being away" being two things actually:


  Laumann et al. (2001) found a five factor structure in their data
  gathered with the RCS, largely in line with the four factor structure as
  proposed by Kaplan and Kaplan (1989). However, the being away
  factor split into two factors: a physical component (referred to as
  novelty), and a psychological component (referred to as escape). This
  finding seems plausible, because Kaplan and Kaplan’s definition of
  being away also has two components: a physical component (being in
  different setting than usual), and a psychological component (being
  able to escape from unwanted distractions and reminders of your
  daily obligations). So, the distinction between the two being away
  components is plausible both theoretically and empirically.


This five factor model has been mostly confirmed in subsequent research, e.g. by Pals et al. (2009) but not all factors seem to come up in some contrasts; most doubt being about compatibility. And there has been further investigation from that group on how fascination actually works.