Try this, the ColorAnimation elements in the storyboards are what you will want to play with. I have it set to ramp up quickly (0.5 sec) but fade out slower (2 sec) so you can see it.
<ListView>
<ListView.Resources>
<Style TargetType="{x:Type ListViewItem}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ListBoxItem}">
<Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="True">
<ContentPresenter ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" ContentStringFormat="{TemplateBinding ContentStringFormat}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
</Border>
<ControlTemplate.Triggers>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsMouseOver" Value="True"/>
</MultiTrigger.Conditions>
<MultiTrigger.EnterActions>
<BeginStoryboard>
<Storyboard>
<ColorAnimation Storyboard.TargetName="Bd" Storyboard.TargetProperty="Background.Color" To="{x:Static SystemColors.HighlightColor}" Duration="00:00:00.5" />
</Storyboard>
</BeginStoryboard>
</MultiTrigger.EnterActions>
<MultiTrigger.ExitActions>
<BeginStoryboard>
<Storyboard>
<ColorAnimation Storyboard.TargetName="Bd" Storyboard.TargetProperty="Background.Color" To="Transparent" Duration="00:00:02" />
</Storyboard>
</BeginStoryboard>
</MultiTrigger.ExitActions>
<Setter Property="Background" TargetName="Bd" Value="Transparent"/>
<Setter Property="BorderBrush" TargetName="Bd" Value="Transparent"/>
</MultiTrigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="Selector.IsSelectionActive" Value="False"/>
<Condition Property="IsSelected" Value="True"/>
</MultiTrigger.Conditions>
<Setter Property="Background" TargetName="Bd" Value="#3DDADADA"/>
<Setter Property="BorderBrush" TargetName="Bd" Value="#FFDADADA"/>
</MultiTrigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="Selector.IsSelectionActive" Value="True"/>
<Condition Property="IsSelected" Value="True"/>
</MultiTrigger.Conditions>
<Setter Property="Background" TargetName="Bd" Value="#3D26A0DA"/>
<Setter Property="BorderBrush" TargetName="Bd" Value="#FF26A0DA"/>
</MultiTrigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="TextElement.Foreground" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</ListView.Resources>
<ListView.Items>
<ListViewItem>
<TextBlock Text="Item 1" />
</ListViewItem>
<ListViewItem>
<TextBlock Text="Item 2" />
</ListViewItem>
<ListViewItem>
<TextBlock Text="Item 3" />
</ListViewItem>
<ListViewItem>
<TextBlock Text="Item 4" />
</ListViewItem>
<ListViewItem>
<TextBlock Text="Item 5" />
</ListViewItem>
</ListView.Items>
</ListView>